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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2011	Oct. 31, 2011
Entity Information [Line Items]
Entity Registrant Name	BLACK HILLS CORP /SD/
Entity Central Index Key	0001130464
Document Type	10-Q
Document Period End Date	Sep. 30, 2011
Amendment Flag	false
Document Fiscal Year Focus	2010
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		39,468,273

Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating revenue:
Utilities	$ 223,714	$ 212,193	$ 834,463	$ 821,027
Non-regulated energy	32,746	37,301	98,422	111,305
Total operating revenues	256,460	249,494	932,885	932,332
Utilities -
Fuel, purchased power and cost of gas sold	86,127	86,933	400,465	420,747
Operations and maintenance	58,313	57,294	184,411	188,357
Gain on sale of operating assets	0	(6,238)	0	(8,921)
Non-regulated energy operations and maintenance	27,898	26,018	85,468	74,084
Depreciation, depletion and amortization	33,374	30,036	97,695	88,691
Taxes - property, production and severance	9,050	7,426	24,510	20,142
Other operating expenses	259	83	562	753
Total operating expenses	215,021	201,552	793,111	783,853
Operating income	41,439	47,942	139,774	148,479
Interest charges -
Interest expense incurred (including amortizationof debt issuance costs, premiums and discounts, realized settlements on interest rate swaps)	(29,697)	(27,827)	(88,418)	(78,941)
Allowance for funds used during construction - borrowed	3,520	1,934	9,874	7,804
Capitalized interest	2,981	1,614	8,198	2,470
Interest rate swap - unrealized (loss) gain	(38,246)	(13,710)	(40,608)	(41,663)
Interest income	563	199	1,598	529
Allowance for funds used during construction - equity	189	375	676	2,663
Other income, net	524	539	1,761	2,225
Total other income (expense)	(60,166)	(36,876)	(106,919)	(104,913)
Income (loss) before equity in earnings (loss) of unconsolidated subsidiaries and income taxes	(18,727)	11,066	32,855	43,566
Equity in earnings (loss) of unconsolidated subsidiaries	43	(137)	1,076	1,471
Income tax benefit (expense)	8,159	1,461	(9,794)	(9,872)
Net income (loss)	$ (10,525)	$ 12,390	$ 24,137	$ 35,165
Weighted average common shares outstanding:
Basic	39,145	38,933	39,105	38,895
Diluted	39,145	39,133	39,792	39,052
Earnings (Loss) Per Share, Basic-
Earnings (loss) per share - basic	$ (0.27)	$ 0.32	$ 0.62	$ 0.9
Earnings (Loss) Per Share, Diluted-
Earnings (loss) per share - diluted	(0.27)	0.32	0.61	0.9
Dividends paid per share of common stock	$ 0.365	$ 0.360	$ 1.095	$ 1.08

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Current assets:
Cash and cash equivalents	$ 74,779	$ 32,438	$ 58,975
Restricted cash	4,080	4,260	17,082
Accounts receivable, net	241,831	328,811	234,480
Materials, supplies and fuel	134,463	139,677	145,251
Derivative assets, current	48,727	56,572	71,688
Income tax receivable, net	10,958	0	25,156
Deferred income tax assets, current	39,628	17,113	15,073
Regulatory assets, current	45,713	66,429	55,941
Other current assets	65,889	25,571	20,932
Total current assets	666,068	670,871	644,578
Investments	17,338	17,780	17,981
Property, plant and equipment	3,664,967	3,359,762	3,243,641
Less accumulated depreciation and depletion	(934,112)	(864,329)	(880,938)
Total property, plant and equipment, net	2,730,855	2,495,433	2,362,703
Other assets:
Goodwill	354,831	354,831	353,734
Intangible assets, net	3,899	4,069	4,129
Derivative assets, non-current	17,215	9,260	12,762
Regulatory assets, non-current	142,267	138,405	124,134
Other assets, non-current	20,894	20,860	20,216
Total other assets	539,106	527,425	514,975
TOTAL ASSETS	3,953,367	3,711,509	3,540,237
Current liabilities:
Accounts payable	219,167	279,069	201,072
Accrued liabilities	168,640	170,301	166,977
Derivative liabilities, current	129,163	79,167	108,318
Accrued income taxes, net	0	779	0
Regulatory liabilities, current	10,568	3,943	12,368
Notes Payable	359,000	249,000	145,000
Current maturities of long-term debt	2,893	5,181	5,314
Total current liabilities	889,431	787,440	639,049
Long-term debt, net of current maturities	1,282,194	1,186,050	1,188,293
Deferred credits and other liabilities:
Deferred income tax liabilities, non-current	329,833	277,136	279,315
Derivative liabilities, non-current	26,603	21,361	25,892
Regulatory liabilities, non-current	85,074	84,611	79,393
Benefit plan liabilities	124,214	124,709	122,178
Other deferred credits and other liabilities	128,013	129,932	125,710
Total deferred credits and other liabilities	693,737	637,749	632,488
Stockholders' equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 39,491,616, 39,280,048 and 39,243,257 shares, respectively	39,492	39,280	39,243
Additional paid-in capital	604,945	598,805	597,108
Retained earnings	467,043	486,075	466,691
Treasury stock at cost – 28,041, 10,962 and 7,905 share, respectively	(810)	(309)	(226)
Accumulated other comprehensive Income (loss)	(22,665)	(23,581)	(22,409)
Total stockholders' equity	1,088,005	1,100,270	1,080,407
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	3,953,367	3,711,509	3,540,237
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Current assets:
Cash and cash equivalents	74,779	32,438	58,975
Restricted cash	4,080	4,260	17,082
Current liabilities:
Notes Payable	$ 359,000	$ 249,000	$ 145,000

Condensed Consolidated Balance Sheets (Parentheticals) - $ / shares	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Common Stock Par Value	$ 1	$ 1	$ 1
Common Stock, Shares Authorized	100,000,000	100,000,000	100,000,000
Common Stock, Shares, Issued	39,491,616	39,280,048	39,243,257
Treasury Stock, Shares	28,041	10,962	7,905

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Operating activities:
Net income (loss)	$ 24,137	$ 35,165
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	97,695	88,691
Derivative fair value adjustments	9,605	(10,690)
Gain on sale of operating assets	0	(8,921)
Stock compensation	4,931	2,908
Unrealized mark-to-market loss (gain) on interest rate swaps	40,608	41,663
Deferred income taxes	26,280	32,366
Equity in (earnings) loss of unconsolidated subsidiaries	(1,076)	(1,471)
Allowance for funds used during construction - equity	(676)	(2,663)
Employee benefit plans	10,930	12,214
Other, net	9,702	6,663
Changes in certain operating assets and liabilities:
Materials, supplies and fuel	12,592	(40,344)
Accounts receivable and other current assets	29,631	8,754
Accounts payable and other current liabilities	(73,489)	(21,295)
Regulatory assets	22,357	(2,205)
Regulatory liabilities	5,041	7,176
Contributions to defined pension plans	(11,050)	(30,015)
Other operating activities	(691)	7,765
Net cash provided by operating activities	206,527	125,761
Investing activities:
Property, plant and equipment additions	(328,496)	(323,883)
Proceeds from sale of operating assets	583	68,105
Payment for acquisition of assets	0	(2,250)
Other investing activities	1,051	4,273
Net cash provided by (used in) investing activities	(326,862)	(253,755)
Financing activities:
Dividends paid	(43,169)	(42,331)
Common stock issued	2,199	3,073
Short-term borrowings - issuances	770,000	451,500
Short-term borrowings - repayments	(560,000)	(471,000)
Long-term debt - issuances	0	200,000
Long-term debt - repayments	(6,169)	(57,550)
Other financing activities	(185)	(9,624)
Net cash provided by (used in) financing activities	162,676	74,068
Net change in cash and cash equivalents	42,341	(53,926)
Cash and cash equivalents:
Cash and cash equivalents, beginning of period	32,438	112,901
Cash and cash equivalents, end of period	$ 74,779	$ 58,975

Management's Statement	9 Months Ended
Management's Statement	Sep. 30, 2011
Management's Statement [Abstract]
Management's Statement	MANAGEMENT'S STATEMENT The condensed consolidated financial statements included herein have been prepared by Black Hills Corporation together with our subsidiaries (the "Company," "us," "we," or "our") without audit, pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations; however, we believe that the footnotes adequately disclose the information presented. These condensed quarterly financial statements should be read in conjunction with the financial statements and the notes thereto included in our 2010 Annual Report on Form 10-K filed with the SEC. Accounting methods historically employed require certain estimates as of interim dates. The information furnished in the accompanying condensed quarterly financial statements reflects all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the September 30, 2011, December 31, 2010 and September 30, 2010 financial information and are of a normal recurring nature. Certain industries in which we operate are highly seasonal and revenue from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Demand for electricity and natural gas is sensitive to seasonal cooling, heating and industrial load requirements, as well as changes in market price. In particular, the normal peak usage season for gas utilities is November through March and significant earnings variances can be expected between the Gas Utilities segment's peak and off-peak seasons. Due to this seasonal nature, our results of operations for the three and nine months ended September 30, 2011 and September 30, 2010, and our financial condition as of September 30, 2011, December 31, 2010, and September 30, 2010 are not necessarily indicative of the results of operations and financial condition to be expected as of or for any other period. All earnings per share amounts discussed refer to diluted earnings per share unless otherwise noted. Certain prior year data presented in the accompanying condensed consolidated financial statements has been reclassified to conform to the current year presentation. Specifically, (a) the Company has reclassified revenue into two categories: Utilities revenue and Non-regulated energy revenue, (b) the categories of Fuel, purchased power and cost of gas sold and Operations and maintenance included in our Operating expenses have been reclassified into Utilities and Non-regulated energy, and (c) the Taxes - property, production and severance line has been reclassified to show only those taxes. Any taxes other than property, production and severance are now included in the respective Utility or Non-regulated energy operations and maintenance lines. Income taxes remain as a separate line item. These reclassifications had no effect on total assets, net income, cash flows or earnings per share. Restatement - Subsequent to the issuance of the Company's 2010 consolidated financial statements, the Company's management determined that certain intercompany transactions with our rate regulated operations had not been properly eliminated in consolidation, resulting in an overstatement of Utility and Non-regulated energy revenue and Fuel, purchased power and cost of gas sold of $14.8 million and $45.6 million, in aggregate for the three and nine months ended September 30, 2010, respectively. As such, the condensed consolidated financial statements have been restated for the correction of this error. The correction did not have an impact on our gross margin, net income, total assets or cash flows.

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

+ References

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+ Details

Recently Adopted and Recently Issued Accounting Standards and Legislation	9 Months Ended
	Sep. 30, 2011
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted and Recently Issued Accounting Standards and Legislation	RECENTLY ADOPTED AND RECENTLY ISSUED ACCOUNTING STANDARDS AND LEGISLATION Recently Adopted Accounting Standards and Legislation Fair Value Measurements, ASC 820 In January 2010, the FASB issued guidance related to improving disclosures about fair value measurements. The guidance requires separate disclosures of the amounts of transfers in and out of Level 1 and Level 2 fair value measurements, disclosure of inputs and techniques used in valuation and a description of the reason for such transfers. In the reconciliation for Level 3 fair value measurements using significant unobservable inputs, information about purchases, sales, issuances and settlements is required to be presented separately. These disclosures are required for interim and annual reporting periods and were effective for us on January 1, 2010, except for the disclosures related to the purchases, sales, issuances and settlements in the roll forward activity of Level 3 fair value measurements, which were effective on January 1, 2011. The guidance required additional disclosures, but did not impact our financial position, results of operations or cash flows. The additional disclosures are included in Note 13 of these Notes to Condensed Consolidated Financial Statements. Patient Protection and Affordable Care Act In March 2010, the President of the United States signed into law comprehensive healthcare reform legislation under the PPACA as amended by the Healthcare and Education Reconciliation Act. The total potential impact on the Company, if any, cannot be determined until regulations are promulgated under the PPACA. Included among the provisions of the PPACA is a change in the tax treatment of the Medicare Part D subsidy (the "subsidy"), which affects our Non-Pension Postretirement Benefit Plan. Internal Revenue Code Section 139A has been amended to eliminate the deduction of the subsidy in reducing income for years beginning after December 31, 2012. The impact of this change in the tax treatment of the subsidy had an immaterial effect on our financial position, results of operations and cash flows. The Company will continue to assess the implications on our financial statements of the PPACA as related regulations and interpretations become available. Recently Issued Accounting Standards and Legislation Intangibles - Goodwill and Other, ASU No. 2011-08 The FASB issued an accounting standards update amending ASC 350 which permits entities to first assess qualitative factors to determine whether it is necessary to perform the two-step goodwill impairment test. If an entity believes, as a result of its qualitative assessment, that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, the quantitative two-step goodwill impairment test is required. An entity has the unconditional option to bypass the qualitative assessment and proceed directly to performing the first step of the goodwill impairment test. ASU 2011-08 is effective for annual and interim goodwill impairment tests performed in fiscal years beginning after December 15, 2011 with early adoption permitted. Other Comprehensive Income, ASU No. 2011-05 FASB issued an accounting standards update amending ASC 220 to improve the comparability, consistency and transparency of reporting of comprehensive income. The update amends existing guidance by allowing only two options for presenting the components of net income and other comprehensive income: (1) in a single continuous financial statement, statement of comprehensive income or (2) in two separate but consecutive financial statements, consisting of an income statement followed by a separate statement of other comprehensive income. Also, items that are reclassified from other comprehensive income to net income must be presented on the face of the financial statements. ASU No. 2011-05 requires retrospective application, and it is effective for fiscal years, and interim periods within those years, beginning after December 15, 2011, with early adoption permitted. The adoption of this update may change the order in which certain financial statements are presented and provide additional detail on those financial statements when applicable, but will not have any other impact on our consolidated financial statements. Fair Value Measurement, ASU No. 2011-04 FASB issued an accounting standards update amending ASC 820 to achieve common fair value measurement and disclosure requirements between GAAP and IFRS. Additional disclosure requirements in the update include: (1) for Level 3 fair value measurements, quantitative information about unobservable inputs used, a description of the valuation processes used by the entity, and a qualitative discussion about the sensitivity of the measurements to changes in the unobservable inputs; (2) for an entity's use of a non-financial asset that is different from the asset's highest and best use, the reason for the difference; (3) for financial instruments not measured at fair value but for which disclosure of fair value is required, the fair value hierarchy level in which the fair value measurements were determined; and (4) the disclosure of all transfers between Level 1 and Level 2 of the fair value hierarchy. ASU No. 2011-04 is effective for fiscal years, and interim periods within those years, beginning after December 31, 2011, with early adoption permitted. We do not expect this amendment to have an impact on our financial position, results of operations, or cash flows. Dodd-Frank Wall Street Reform and Consumer Protection Act In July 2010, the President of the United States signed into law comprehensive financial reform legislation under Dodd-Frank. Title VII of Dodd-Frank effectively regulates many derivative transactions in the United States that were previously unregulated, including swap transactions in the over-the-counter market. Among other things, Dodd-Frank (i) mandates the clearing of some swaps through regulated central clearing organizations and the trading of clearing swaps through regulated exchanges or swap execution facilities, in each case subject to certain key exemptions, and (ii) authorizes regulators to establish collateral and margin requirements for certain swap transactions that are not cleared. Dodd-Frank provides for a potential exception from these clearing and cash collateral requirements for commercial end-users, and includes a number of defined terms that will be used in determining how this exception applies to particular derivative transactions and the parties to those transactions. Significant rule-making by numerous governmental agencies, particularly the CFTC with respect to non-security commodities, will be required in order to implement the restrictions, limitations, and requirements contemplated by Dodd-Frank. We will continue to evaluate the impact as these rules become available.

Supplemental Disclosure of Cash Flow Information

9 Months Ended

Sep. 30, 2011

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosure of Cash Flow Information

SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION



	Nine Months Ended
	September 30, 2011			September 30, 2010
	(in thousands)
Non-cash investing activities—
Property, plant and equipment acquired with accrued liabilities	$	49,566		$	37,661
Cash (paid) refunded during the period for—
Interest (net of amounts capitalized)	$	(61,461	)	$	(62,740	)
Income taxes, net	$	11,826		$	(488	)

Materials, Supplies and Fuel

9 Months Ended

Sep. 30, 2011

Inventory, Net [Abstract]

Materials, Supplies and Fuel

MATERIALS, SUPPLIES AND FUEL

The amounts of materials, supplies and fuel included in the accompanying Condensed Consolidated Balance Sheets, by major classification, were as follows (in thousands):



	September 30, 2011		December 31, 2010		September 30, 2010
Materials and supplies	$	37,611	$	31,749	$	31,192
Fuel - Electric Utilities	8,639		9,687		9,056
Natural gas in storage — Gas Utilities	38,641		21,691		36,782
Commodities held by Energy Marketing*	49,572		76,550		68,221
Total materials, supplies and fuel	$	134,463	$	139,677	$	145,251

_____________

* As of September 30, 2011, December 31, 2010 and September 30, 2010, market adjustments related to natural gas held by Energy Marketing and recorded in inventory as part of fair value hedge transactions were $(1.7) million, $(9.1) million and $(18.7) million, respectively (see Note 12 for further discussion of Energy Marketing activities).

Accounts Receivable

9 Months Ended

Sep. 30, 2011

Receivables [Abstract]

Accounts Receivable

ACCOUNTS RECEIVABLE

Trade Accounts Receivable

Our Accounts receivable represents primarily customer trade accounts at our Electric Utilities and Gas Utilities segments and counterparty trade accounts at our Energy Marketing segment. This balance fluctuates primarily due to the seasonality of our Gas Utilities and volume and commodity prices at our Energy Marketing segment. We maintain an allowance for doubtful accounts that reflects our best estimate of probable uncollectible trade receivables. We regularly review our trade receivable allowances by considering such factors as historical experience, credit worthiness, the age of the receivable balances and current economic conditions that may affect our ability to collect.

Following is a summary of receivables (in thousands):



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
September 30, 2011	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	41,889	$	16,401	$	58,290	$	(590	)	$	57,700
Gas	21,168		12,518		33,686		(789		)	32,897
Oil and Gas	8,820		—		8,820		(161		)	8,659
Coal Mining	1,845		—		1,845		—			1,845
Energy Marketing	139,332		—		139,332		(174		)	139,158
Power Generation	119		—		119		—			119
Corporate	1,453		—		1,453		—			1,453
Total	$	214,626	$	28,919	$	243,545	$	(1,714	)	$	241,831



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
December 31, 2010	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	51,005	$	19,572	$	70,577	$	(708	)	$	69,869
Gas	41,970		40,376		82,346		(1,425		)	80,921
Oil and Gas	6,213		—		6,213		(161		)	6,052
Coal Mining	2,420		—		2,420		—			2,420
Energy Marketing	157,064		—		157,064		(69		)	156,995
Power Generation	307		—		307		—			307
Corporate (a)	12,247		—		12,247		—			12,247
Total	$	271,226	$	59,948	$	331,174	$	(2,363	)	$	328,811



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
September 30, 2010	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	41,955	$	17,959	$	59,914	$	(927	)	$	58,987
Gas	19,611		11,107		30,718		(830		)	29,888
Oil and Gas	6,112		—		6,112		(161		)	5,951
Coal Mining	2,201		—		2,201		—			2,201
Energy Marketing	99,850		—		99,850		(375		)	99,475
Power Generation	463		—		463		—			463
Corporate ^{(a) (b)}	37,515		—		37,515		—			37,515
Total	$	207,707	$	29,066	$	236,773	$	(2,293	)	$	234,480

(a) During the third quarter of 2010 we reached a settlement with the IRS and received a refund relating to this settlement during 2011 of $12.0 million, excluding interest income.

(b) includes cash collateral receivable on de-designated interest rate swaps. See Note 12 for further information.

- Definition

The entire disclosure for claims held for amounts due a company. Examples include trade accounts receivables, notes receivables, loans receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 3, 4
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 7
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 01-6
-Paragraph 13
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 4
-Section 08
-Paragraph k

Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02.3,4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
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-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5074-111524

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5066-111524

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5162-111524

+ Details

Notes Payable

9 Months Ended

Sep. 30, 2011

Notes Payable [Abstract]

Notes Payable

NOTES PAYABLE

Our credit facilities and debt securities contain certain restrictive covenants including, among others, recourse leverage ratios and consolidated net worth covenants. As of September 30, 2011, we were in compliance with these covenants. Our credit facilities and debt securities do not contain default provisions pertaining to our credit ratings.

We had the following short-term debt issued and outstanding as of the Condensed Consolidated Balance Sheet dates (in thousands):



	As of September 30, 2011				As of December 31, 2010				As of September 30, 2010
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	209,000	$	42,355	$	149,000	$	46,900	$	145,000	$	15,500
Enserco Credit Facility	—		132,625		—		166,900		—		131,500
Term Loan due 2011	—		—		100,000		—		—		—
Term Loan due 2012	150,000		—		—		—		—		—
Total	$	359,000	$	174,980	$	249,000	$	213,800	$	145,000	$	147,000

Revolving Credit Facility

Our $500.0 million Revolving Credit Facility expiring April 14, 2013 contains an accordion feature which allows us, with the consent of the administrative agent, to increase the capacity of the facility to $600.0 million and can be used for the issuance of letters of credit, to fund working capital needs and for other corporate purposes. Borrowings are available under a base rate option or a Eurodollar option. The cost of borrowings or letters of credit is determined based upon our credit ratings. At current ratings levels, the margins for base rate borrowings, Eurodollar borrowings and letters of credit were 1.75%, 2.75% and 2.75%, respectively, at September 30, 2011. The facility contains a commitment fee to be charged on the unused amount of the facility. Based upon current credit ratings, the fee is 0.5%.

Deferred financing costs are being amortized over the term of the facility. The amortization expense is included in Interest expense on the accompanying Condensed Consolidated Statements of Income as follows (in thousands):



	Deferred Financing	Amortization Expense
	Costs Remaining on Balance Sheet as of	Three Months Ended September 30,				Nine Months Ended September 30,
	September 30, 2011	2011		2010		2011		2010
Deferred Financing Costs - Revolving Credit Facility	$1,970	$	473	$	481	$	1,419	$	866

The Revolving Credit Facility includes the following covenants that we must comply with at the end of each quarter (dollars in thousands). We were in compliance with these covenants as of September 30, 2011.



As of September 30, 2011	Actual			Covenant Requirement
Consolidated Net Worth	$	1,088,000		$	871,300
Recourse Leverage Ratio	61.3		%	65.0		%

Enserco Credit Facility

Enserco's $250.0 million committed credit facility expiring May 7, 2012 contains an accordion feature which allows, with the consent of the administrative agent, the commitment under the facility to increase to $350.0 million. Maximum borrowings under the facility are subject to a sub-limit of $50.0 million. Borrowings under this facility are available under a base rate option or a Eurodollar option. Margins for base rate borrowings are 1.75% and for Eurodollar borrowings are 2.50%. Enserco Credit Facility covenants include tangible net worth, net working capital and realized net working capital requirements. Enserco was in compliance with these covenants as of September 30, 2011.

Deferred financing costs for the Enserco Credit Facility are being amortized over the term of the Enserco Credit Facility. The amortization expense is included in Interest expense on the accompanying Condensed Consolidated Statements of Income as follows (in thousands):



		Amortization Expense
	Deferred Financing Costs Remaining on Balance Sheet as of	Three Months Ended September 30,				Nine Months Ended September 30,
	September 30, 2011	2011		2010		2011		2010
Deferred Financing Costs - Enserco Credit Facility	$812	$	305	$	263	$	866	$	1,245

Corporate Term Loans

On September 30, 2011, we extended our $100.0 million term loan for two-years under the existing terms. This term loan is now due on September 30, 2013.

In June 2011, we entered into a one-year $150.0 million unsecured, single draw, term loan with CoBank, the Bank of Nova Scotia and U.S. Bank due on June 24, 2012. The cost of borrowing under the loan is based on a spread of 125 basis points over LIBOR (1.63% at September 30, 2011). The covenants are substantially the same as those included in the Revolving Credit Facility. We were in compliance with these covenants as of September 30, 2011.

Earnings per Share

9 Months Ended

Sep. 30, 2011

Earnings Per Share [Abstract]

Earnings Per Share

EARNINGS PER SHARE

Basic earnings (loss) per share is computed by dividing net income by the weighted-average number of common shares outstanding during the period. Diluted earnings (loss) per share is computed by using all dilutive common shares potentially outstanding during a period. A reconciliation of share amounts used to compute earnings (loss) per share is as follows (in thousands):



	Three Months Ended September 30,					Nine Months Ended September 30,
	2011			2010		2011		2010

Net income (loss)	$	(10,525	)	$	12,390	$	24,137	$	35,165

Weighted average shares - basic	39,145			38,933		39,105		38,895
Dilutive effect of:
Restricted stock	—			131		147		110
Stock options	—			12		16		9
Forward equity issuance	—			—		473		—
Other	—			57		51		38
Weighted average shares - diluted	39,145			39,133		39,792		39,052

Below is a discussion of our potentially dilutive shares that were not included in the computation of diluted earnings per share as their effect would have been anti-dilutive.

Due to the Company's net loss in the quarter ending September 30, 2011, potentially dilutive securities, consisting of outstanding stock options, restricted common stock, restricted stock units, non-vested performance-based share awards, warrants and forward equity instruments were excluded from the diluted loss per share calculation due to their anti-dilutive effect. In computing diluted net loss per share, 11,880 options to purchase shares of common stock, 159,873 vested and non-vested restricted stock shares, 31,408 warrants and other performance shares and 424,715 forward equity instruments were excluded from the computations for the three months ended September 30, 2011.

In addition to these potentially dilutive shares, the following outstanding securities were not included in the computation of diluted earnings per share as their effect would have been anti-dilutive (in thousands):



	Three Months Ended September 30,		Nine Months Ended September 30,
	2011	2010	2011	2010
Stock options	176	128	119	169
Restricted stock	20	2	17	2
Other stock	27	1	19	1
Anti-dilutive shares	223	131	155	172

Comprehensive Income (Loss)

9 Months Ended

Sep. 30, 2011

Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]

Comprehensive Income (Loss)

COMPREHENSIVE INCOME (LOSS)

The following table presents the components of our comprehensive income (loss) (in thousands):



	Three Months Ended September 30, 2011
Net income (loss)				$	(10,525	)
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	3,137
Taxes on fair value adjustment on derivatives designated as cash flow hedges	(1,215		)
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,922

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	414
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	(129		)
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				285

Comprehensive income (loss)				$	(8,318	)



	Three Months Ended September 30, 2010
Net income (loss)				$	12,390
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	517
Taxes on fair value adjustment on derivatives designated as cash flow hedges	486
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,003

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	(4,730	)
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	1,761
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				(2,969		)

Comprehensive income (loss)				$	10,424



	Nine Months Ended September 30, 2011
Net income (loss)				$	24,137
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	(1,644	)
Taxes on fair value adjustment on derivatives designated as cash flow hedges	653
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				(991		)

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	2,892
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	(985		)
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				1,907

Comprehensive income (loss)				$	25,053



	Nine Months Ended September 30, 2010
Net income (loss)				$	35,165
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	(8	)
Taxes on benefit plan liability adjustments	(7		)
Benefit plan liability adjustments, net of tax				(15		)

Fair value adjustment on derivatives designated as cash flow hedges	$	495
Taxes on fair value adjustment on derivatives designated as cash flow hedges	641
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,136

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	(6,909	)
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	2,543
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				(4,366		)

Comprehensive income (loss)				$	31,920

Balances by classification included within Accumulated other comprehensive income (loss) on the accompanying Condensed Consolidated Balance Sheets are as follows (in thousands):



	September 30, 2011			December 31, 2010			September 30, 2010
Derivatives designated as cash flow hedges	$	(11,523	)	$	(12,437	)	$	(12,741	)
Benefit plans	(11,142		)	(11,142		)	(9,636		)
Amount from equity-method investees	—			(2		)	(32		)
Total	$	(22,665	)	$	(23,581	)	$	(22,409	)

- Definition

The entire disclosure for comprehensive income. Includes, but is not limited to, the following: 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income. Components of comprehensive income include: (1) foreign currency translation adjustments; (2) gains (losses) on foreign currency transactions that are designated as, and are effective as, economic hedges of a net investment in a foreign entity; (3) gains (losses) on intercompany foreign currency transactions that are of a long-term-investment nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements; (4) change in the market value of a futures contract that qualifies as a hedge of an asset reported at fair value; (5) unrealized holding gains (losses) on available-for-sale securities and that resulting from transfers of debt securities from the held-to-maturity category to the available-for-sale category; (6) a net loss recognized as an additional pension liability not yet recognized as net periodic pension cost; and (7) the net gain (loss) and net prior service cost or credit for pension plans and other postretirement benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 14-26
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e653-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e689-108580

+ Details

Common Stock

9 Months Ended

Sep. 30, 2011

Common Stock, Including Additional Paid in Capital, Net of Discount [Abstract]

Common Stock

COMMON STOCK

Other than the following transactions, we had no material changes in our common stock during the nine months ended September 30, 2011 from the amount reported in Note 11 of the Notes to Consolidated Financial Statements in our 2010 Annual Report on Form 10-K.

Equity Compensation Plans

•

We granted 67,389 target performance shares to certain officers and business unit leaders for the January 1, 2011 through December 31, 2013 performance period during the nine months ended September 30, 2011. Actual shares are issued after the end of the performance plan period. Performance shares are awarded based on our total stockholder return over the designated performance period as measured against a selected peer group and can range from 0% to 175% of target. In addition, certain stock price performance must be achieved for a payout to occur. The final value of the performance shares will vary according to the number of shares of common stock that are ultimately granted based upon the actual level of attainment of the performance criteria. The performance awards are paid 50% in the form of cash and 50% in shares of common stock. The grant date fair value was $25.91 per share.


•	We issued 14,111 shares of common stock under our short-term incentive compensation plan during the nine months ended September 30, 2011. Pre-tax compensation cost related to the awards was approximately $0.4 million, which was expensed in 2010.


•	We granted 136,348 shares of restricted common stock and restricted stock units during the nine months ended September 30, 2011. The pre-tax compensation cost related to the awards of restricted stock and restricted stock units of approximately $4.1 million will be recognized over the three year vesting period.


•	We granted 99,000 stock options at a weighted-average exercise price of $32.04 during the nine months ended September 30, 2011. The total fair value of approximately $0.6 million will be recognized over the three year vesting period.


•	Stock options totaling 5,500 shares were exercised during the nine months ended September 30, 2011 at a weighted-average exercise price of $29.94 per share, providing $0.2 million of proceeds.

Total compensation expense recognized for all equity compensation plans for the three months ended September 30, 2011 and 2010 was $1.7 million and $1.9 million, respectively, and for the nine months ended September 30, 2011 and 2010 was $5.0 million and $4.7 million, respectively.

As of September 30, 2011, total unrecognized compensation expense related to non-vested stock awards was $8.5 million and is expected to be recognized over a weighted-average period of 2 years.

Dividend Reinvestment and Stock Purchase Plan

We have a Dividend Reinvestment and Stock Purchase Plan ("DRIP") under which stockholders may purchase additional shares of common stock through dividend reinvestment and/or optional cash payments at 100% of the recent average market price. We have the option of issuing new shares or purchasing the shares on the open market. We issued 79,339 new shares at a weighted-average price of $30.81 during the nine months ended September 30, 2011. At September 30, 2011, 476,437 shares of unissued common stock were available for future offering under the DRIP.

Dividend Restrictions

Our Revolving Credit Facility contains restrictions on the payment of cash dividends upon a default or event of default. An event of default would be deemed to have occurred if we did not meet certain financial covenants. The most restrictive financial covenants include the following: a recourse leverage ratio not to exceed 0.65 to 1.00 and a minimum consolidated net worth of $625 million plus 50.0% of aggregate consolidated net income, if positive, since January 1, 2005. As of September 30, 2011, we were in compliance with these covenants.

Due to our holding company structure, substantially all of our operating cash flows are provided by dividends paid or distributions made by our subsidiaries. The cash to pay dividends to our stockholders is derived from these cash flows. As a result, certain statutory limitations or regulatory or financing agreements could affect the levels of distributions allowed to be made by our subsidiaries. The following restrictions on distributions from our subsidiaries existed as of September 30, 2011:


•	Our utility subsidiaries are generally limited to the amount of dividends allowed by state regulatory authorities to be paid to us as a utility holding company and also may be subject to further restrictions under the Federal Power Act. As of September 30, 2011, the restricted net assets at our Utilities Group were approximately $164.3 million.

•

Our Enserco credit facility is a borrowing base credit facility, the structure of which requires certain levels of tangible net worth and net working capital to be maintained for a given borrowing base election level. In order to maintain a borrowing base election level, Enserco may be restricted from making dividend payments to its parent company. Enserco's restricted net assets at September 30, 2011 were $163.8 million.


•	Pursuant to a covenant in the Black Hills Wyoming project financing, Black Hills Non-regulated Holdings has restricted assets of $100.0 million. Black Hills Non-regulated Holdings is the parent of Black Hills Electric Generation, which is the parent of Black Hills Wyoming.

Forward Equity Instrument

In November 2010, we entered into a Forward Equity Agreement in connection with a public offering of 4,000,000 shares of Black Hills Corporation common stock. In December 2010, the underwriters exercised the over-allotment option to purchase an additional 413,519 shares under the same terms as the original Forward Equity Agreement. We settled the equity forward instrument on November 1, 2011 by physically delivering 4,413,519 shares of common stock in exchange for proceeds of approximately $120 million.

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 4
-Section 08
-Paragraph d

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 1
-Section B
-Paragraph 7, 11A
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 3, 4, 5, 6, 7, 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
-Paragraph 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 10: http://www.xbrl.org/2003/role/presentationRef
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-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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+ Details

Employee Benefit Plans

9 Months Ended

Sep. 30, 2011

Employee Benefit Plans [Abstract]

Employee Benefit Plans

EMPLOYEE BENEFIT PLANS

Defined Benefit Pension Plans

We have three non-contributory defined benefit pension plans (the "Pension Plans"). One covers certain eligible employees of the following subsidiaries: Black Hills Service Company, Black Hills Power, WRDC and BHEP; one covers certain eligible employees of Cheyenne Light, and one Pension Plan covers certain eligible employees of Black Hills Energy. The Pension Plan benefits are based on years of service and compensation levels.

The components of net periodic benefit cost for the Pension Plans were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Service cost	$	1,355		$	1,533		$	4,066		$	4,599
Interest cost	3,732			3,773			11,196			11,319
Expected return on plan assets	(4,239		)	(3,623		)	(12,717		)	(10,869		)
Prior service cost	25			305			75			915
Net loss (gain)	1,135			500			3,405			1,500
Curtailment expense	—			—			—			—
Net periodic benefit cost	$	2,008		$	2,488		$	6,025		$	7,464

Non-pension Defined Benefit Postretirement Healthcare Plans

We sponsor the following retiree healthcare plans (the "Healthcare Plans"): the Black Hills Corporation Postretirement Healthcare Plan, the Healthcare Plan for Retirees of Cheyenne Light, and the Black Hills Energy Postretirement Healthcare Plan. Employees who participate in the Healthcare Plans and who retire on or after meeting certain eligibility requirements are entitled to postretirement healthcare benefits.

The components of net periodic benefit cost for the Healthcare Plans were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Service cost	$	375		$	377		$	1,125		$	1,131
Interest cost	542			611			1,626			1,833
Expected return on plan assets	(41		)	(52		)	(123		)	(156		)
Prior service benefit	(120		)	(77		)	(360		)	(231		)
Net transition obligation	—			—			—			—
Net loss (gain)	169			159			507			477
Net periodic benefit cost	$	925		$	1,018		$	2,775		$	3,054

It has been determined that our post-65 retiree prescription drug plans are actuarially equivalent and qualify for the Medicare Part D subsidy.

Supplemental Non-qualified Defined Benefit Plans

We have various supplemental retirement plans for key executives (the "Supplemental Plans"). The Supplemental Plans are non-qualified defined benefit plans.

The components of net periodic benefit cost for the Supplemental Plans were as follows (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2011		2010		2011		2010
Service cost	$	257	$	171	$	771	$	513
Interest cost	324		321		973		963
Prior service cost	1		1		3		3
Net loss (gain)	128		71		383		213
Net periodic benefit cost	$	710	$	564	$	2,130	$	1,692

Contributions

We anticipate that we will make contributions to each of the benefit plans during 2011 and 2012. Contributions to the Healthcare Plans and the Supplemental Plans expected to be made in the form of benefit payments are as follows (in thousands):



	Contributions Made		Contributions Made
	Three Months Ended September 30, 2011		Nine Months Ended September 30, 2011		Contributions Remaining for 2011		Contributions Anticipated for 2012
Defined Benefit Pension Plans	$	10,500	$	11,050	$	—	$	7,869
Non-pension Defined Benefit Postretirement Healthcare Plans	$	882	$	2,646	$	882	$	3,765
Supplemental Non-qualified Defined Benefit Plans	$	235	$	705	$	236	$	896

- Definition

The entire disclosure for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Summary of Information Relating to Segments of our Business

9 Months Ended

Sep. 30, 2011

Segment Reporting Information, Additional Information [Abstract]

Summary of Information Relating to Segments of our Business

SUMMARY OF INFORMATION RELATING TO SEGMENTS OF OUR BUSINESS

Our reportable segments are based on our method of internal reporting, which generally segregates the strategic business groups due to differences in products, services and regulation. As of September 30, 2011, substantially all of our operations and assets were located within the United States.

We conduct our operations through the following six reportable segments:

Utilities Group —


•	Electric Utilities, which supplies electric utility service to areas in South Dakota, Wyoming, Colorado and Montana and natural gas utility service to Cheyenne, Wyoming and vicinity; and


•	Gas Utilities, which supplies natural gas utility service to areas in Colorado, Iowa, Kansas and Nebraska.

Non-regulated Energy Group —


•	Oil and Gas, which produces, explores and operates oil and natural gas interests located in the Rocky Mountain region and other states;

•

Power Generation, which produces and sells power and capacity to wholesale customers from power plants located in Wyoming. Additionally, in 2009 our Power Generation segment entered into a 20-year PPA to supply Colorado Electric with 200 MW of capacity and energy from power plants under construction in Colorado, which are expected to be placed into service by December 31, 2011. In January 2011, we sold our ownership interests in the partnerships which owned the generation facilities in Idaho;


•	Coal Mining, which engages in the mining and sale of coal from our mine near Gillette, Wyoming; and


•	Energy Marketing, which provides natural gas, crude oil, coal, power and environmental marketing and related services in the United States and Canada.

Segment information follows the accounting policies described in Note 1 of the Notes to Consolidated Financial Statements in our 2010 Annual Report on Form 10-K.

Segment information included in the accompanying Condensed Consolidated Statements of Income and Condensed Consolidated Balance Sheets was as follows (in thousands):



Three Months Ended September 30, 2011	External Operating Revenue		Inter-segment Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	151,063	$	2,653		$	15,790
Gas	72,651		—			572
Non-regulated Energy:
Oil and Gas	19,163		—			241
Power Generation	1,011		7,089			337
Coal Mining	9,184		8,651			555
Energy Marketing	3,388		3,550			273
Corporate ^(a)	—		—			(27,943		)
Inter-segment eliminations	—		(21,943		)	(350		)
Total	$	256,460	$	—		$	(10,525	)



Three Months Ended September 30, 2010	External Operating Revenue		Inter-segment Operating Revenue ^(d)			Net Income (Loss)
Utilities:
Electric ^(b)	$	138,761	$	2,884		$	18,537
Gas ^(c)	72,323		—			(595		)
Non-regulated Energy:
Oil and Gas ^(e)	19,354		—			836
Power Generation	1,124		6,731			575
Coal Mining	7,744		6,533			1,673
Energy Marketing	9,060		(87		)	1,370
Corporate ^{(a) (f)}	—		—			(10,093		)
Inter-segment eliminations	—		(14,933		)	87
Total	$	248,366	$	1,128		$	12,390



Nine Months Ended September 30, 2011	External Operating Revenue		Inter-segment Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	431,624	$	9,902		$	34,653
Gas	402,839		—			24,275
Non-regulated Energy:
Oil and Gas	55,907		—			(553		)
Power Generation	2,750		20,750			2,071
Coal Mining	23,064		25,806			(1,124		)
Energy Marketing	16,701		5,178			1,327
Corporate ^(a)	—		—			(36,101		)
Inter-segment eliminations	—		(61,636		)	(411		)
Total	$	932,885	$	—		$	24,137



Nine Months Ended September 30, 2010	External Operating Revenue		Inter-segment Operating Revenue ^(d)			Net Income (Loss)
Utilities:
Electric^(b)	$	415,092	$	11,627		$	35,585
Gas ^(c)	402,608		—			18,017
Non-regulated Energy:
Oil and Gas ^(e)	57,755		—			3,405
Power Generation	3,266		19,336			1,239
Coal Mining	22,431		20,875			6,093
Energy Marketing	27,797		(157		)	4,890
Corporate ^{(a) (f)}	—		—			(34,221		)
Inter-segment eliminations	—		(48,298		)	157
Total	$	928,949	$	3,383		$	35,165

____________

(a) Net income (loss) includes a $24.9 million and a $26.4 million net after-tax mark-to-market loss on interest rate swaps for the three and nine months ended September 30, 2011 and an $8.9 million and $27.1 million net after-tax loss on interest rate swaps for the three and nine months ended September 30, 2010, respectively.

(b) Net income (loss) includes a $4.1 million after-tax gain on sale of a 23% interest in Wygen III to the City of Gillette.

(c) Net income (loss) includes a $1.7 million after-tax gain on sale of operating assets in the Gas Utilities at Nebraska Gas.

(d) Total operating revenue has been restated to reflect elimination of intercompany activities previously not eliminated. See Note 1 for further information.

(e) Net income (loss) includes a $0.4 million reduction of income taxes as a result of a re-measurement of a previously reported uncertain tax position due to a settlement with the IRS.

(f) Net income (loss) includes a $2.0 million reduction in income tax expense reflecting a re-measurement of an uncertain tax position due to a settlement agreement that was reached with the IRS primarily due to tax depreciation method changes.



Total assets	September 30, 2011		December 31, 2010		September 30, 2010
Utilities:
Electric ^(a)	$	1,917,183	$	1,834,019	$	1,771,014
Gas	683,163		722,287		659,801
Non-regulated Energy:
Oil and Gas	405,513		349,991		358,113
Power Generation^(a)	372,313		293,334		249,778
Coal Mining	94,908		96,962		94,149
Energy Marketing	340,499		314,930		287,173
Corporate	139,788		99,986		120,209
Total assets	$	3,953,367	$	3,711,509	$	3,540,237

____________

(a) Includes construction of a 180 MW power generation facility by our Colorado Electric utility and a 200 MW power generation facility by our Power Generation segment; both facilities are currently under construction and are expected to be completed by December 31, 2011.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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+ Details

Risk Management Activities

9 Months Ended

Sep. 30, 2011

Risk Management Activities [Abstract]

Risk Management Activities

RISK MANAGEMENT ACTIVITIES

Our activities in the regulated and non-regulated energy sectors expose us to a number of risks in the normal operation of our businesses. Depending on the activity, we are exposed to varying degrees of market risk and counterparty risk. We have developed policies, processes, systems, and controls to manage and mitigate these risks.

Market risk is the potential loss that might occur as a result of an adverse change in market price or rate. We are exposed to the following market risks:


•	Commodity price risk associated with our marketing businesses, our natural long position with crude oil, natural gas and coal reserves and production, fuel procurement for certain of our gas-fired generation assets and variability in revenue due to changes in gas usage at our Gas Utilities segment and from commodity price changes;


•	Interest rate risk associated with variable rate credit facilities and changes in forward interest rates used to determine the mark-to-market adjustment on our interest rate swaps; and


•	Foreign currency exchange risk associated with marketing transacted in Canadian dollars.

Our exposure to these market risks is affected by a number of factors including the size, duration, and composition of our energy portfolio, the absolute and relative levels of interest rates, currency exchange rates and commodity prices, the volatility of these prices and rates, and the liquidity of the related interest rate and commodity markets.

We actively manage our exposure to certain market risks as described in Note 3 of the Notes to our Consolidated Financial Statements in our 2010 Annual Report on Form 10-K. Our derivative and hedging activities included in the accompanying Condensed Consolidated Balance Sheets and Condensed Consolidated Statements of Income are detailed below and within Note 13.

Trading Activities

Our Energy Marketing segment is engaged in marketing natural gas, crude oil, coal, power and environmental products, specializing in producer services, end-use origination and wholesale marketing in the United States and Canada. Coal marketing activity began June 1, 2010, Power marketing began late in the third quarter of 2010, and Environmental marketing began late in the third quarter of 2010 with no significant activity until the second quarter of 2011.

Contracts and other activities at our Energy Marketing operations are accounted for under the accounting standards for energy trading contracts. As such, all of the contracts and other activities at our marketing operations that meet the definition of a derivative are accounted for at fair value. The fair values are recorded as either Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets. The net gains or losses are recorded as Operating revenue in the accompanying Condensed Consolidated Statements of Income. Accounting for energy trading contracts precludes mark-to-market accounting for energy trading contracts that are not defined as derivatives pursuant to accounting standards for derivatives. As part of our marketing operations, we often employ strategies that include derivative contracts along with inventory, storage and transportation positions to accomplish the objectives of our producer services, end-use origination and wholesale marketing groups. Except in limited circumstances when we are able to designate transportation, storage or inventory positions as part of a fair value hedge, accounting for derivatives and hedging generally does not allow us to mark inventory, transportation or storage positions to market. The result is that while a significant majority of our natural gas, crude oil and coal marketing positions are economically hedged, we are required to mark some parts of our overall strategies (the derivatives) to market value, but are generally precluded from marking the rest of our economic hedges (transportation, inventory or storage) to market. Volatility in reported earnings and derivative positions results from these accounting requirements.

To effectively manage our portfolios, we enter into forward physical commodity contracts, financial derivative instruments including over-the-counter swaps and options, and storage and transportation agreements. The business activities of our Energy Marketing segment are conducted within the parameters as defined and allowed in the BHCRPP and further delineated in the Energy Marketing Risk Management Policies and Procedures as approved by our Executive Risk Committee.

We use a number of quantitative tools to measure, monitor and limit our exposure to market risk in our marketing portfolio. We limit and monitor our market risk through established limits on the nominal size of positions based on type of trade, location and duration. Such limits include those on fixed price, basis, index, storage, transportation and foreign exchange positions.

Daily risk management activities include reviewing positions in relation to established position limits, assessing changes in daily mark-to-market and other non-statistical risk management techniques.

The contract or notional amounts and terms of our marketing activities and derivative commodity instruments were as follows:



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of MMBtus)
Natural gas basis swaps purchased	425,360	42	399,128	22	335,805	25
Natural gas basis swaps sold	443,489	42	426,903	22	358,929	25
Natural gas fixed-for-float swaps purchased	251,602	27	135,005	33	84,636	36
Natural gas fixed-for-float swaps sold	249,808	27	150,803	22	97,210	18
Natural gas physical purchases	105,446	27	144,948	36	135,818	18
Natural gas physical sales	122,232	72	143,021	36	136,530	36
Natural gas futures purchased	78,100	7	—	—	—	—
Natural gas futures sold	96,730	7	—	—	—	—
Natural gas options purchased	6,000	2	—	—	—	—
Natural gas options sold	6,000	2	—	—	—	—



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of Bbls)
Crude oil physical purchases	7,326	15	5,628	16	5,561	15
Crude oil physical sales	7,917	15	6,921	16	4,759	15
Crude oil fixed-for-float swaps purchased	—	—	20	3	135	1
Crude oil fixed-for-float swaps sold	10	2	240	4	289	3



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of tons)
Coal fixed-for-float swaps purchased	8,305	27	4,060	36	5,585	39
Coal fixed-for-float swaps sold	9,710	27	3,720	36	4,445	39
Coal physical purchases	27,982	39	24,634	48	24,100	51
Coal physical sales	13,331	39	9,046	36	6,213	35
Coal options purchased	4,530	51	2,835	48	1,980	27
Coal options sold	572	6	270	12	360	15



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in thousands of MWh):	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Power physical purchases	153	54	—	—	—	—
Power physical sales	153	54	—	—	—	—
Power fixed-for-float swaps purchased	12,370	27	—	—	—	—
Power fixed-for-float swaps sold	12,439	27	—	—	—	—



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in thousands of MWh):	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Environmental products physical purchases	283	54	—	—	—	—
Environmental products physical sales	273	54	—	—	—	—

Derivatives and certain other marketing transactions were marked to fair value at September 30, 2011, December 31, 2010 and September 30, 2010, and the related gains and/or losses recognized in earnings. The amounts included in the accompanying Condensed Consolidated Balance Sheets and Condensed Consolidated Statements of Income were as follows (in thousands):



	September 30, 2011			December 31, 2010			September 30, 2010
Current derivative assets	$	36,550		$	43,862		$	55,366
Non-current derivative assets	$	13,969		$	6,635		$	8,023
Current derivative liabilities	$	27,851		$	14,550		$	17,743
Non-current derivative liabilities	$	4,128		$	3,464		$	1,277
Cash collateral receivable (payable) included in derivative assets/liabilities	$	9,026		$	3,958		$	(7,365	)
Unrealized gains	$	9,514		$	28,525		$	51,734
Net derivative assets (liabilities) with credit risk-related contingent features that require Enserco to maintain a specific credit rating	$	—		$	—		$	—
Cash collateral receivable included in Other current assets	$	34,642		$	9,919		$	1,854
Cash collateral (payable) included in Other current liabilities	$	(802	)	$	(1,079	)	$	(1,079	)

In addition, certain volumes of natural gas inventory have been designated as the underlying hedged item in fair value hedge transactions. These volumes include market adjustments based on published industry quotations. Market adjustments are recorded in Materials, supplies and fuel on the accompanying Condensed Consolidated Balance Sheets and the related unrealized gain or loss on the Condensed Consolidated Statements of Income, effectively offsetting the earnings impact of the unrealized gain or loss recognized on the associated derivative asset or liability described above. As of September 30, 2011, December 31, 2010 and September 30, 2010, the market adjustments recorded in inventory were $(1.7) million, $(9.1) million and $(18.7) million, respectively.

Activities Other Than Trading

Oil and Gas Exploration and Production

We produce natural gas and crude oil through our exploration and production activities. Our natural "long" positions, or unhedged open positions, result in commodity price risk and variability to our cash flows. We employ risk management methods to mitigate this commodity price risk and preserve our cash flows, and we have adopted guidelines covering hedging for our natural gas and crude oil production. These guidelines have been approved by our Executive Risk Committee and are routinely reviewed by our Board of Directors.

We held a portfolio of swaps and options to hedge portions of our crude oil and natural gas production. We elect hedge accounting on those over-the-counter swaps and options. These transactions were designated at inception as cash flow hedges, documented under accounting for derivatives and hedging, and initially met prospective effectiveness testing. Effectiveness of our hedging position is evaluated at least quarterly.

The derivatives were marked to fair value and are recorded as Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets. The effective portion of the gain or loss on these derivatives is reported in Accumulated other comprehensive income (loss) and the ineffective portion, if any, is reported in earnings.

We had the following derivatives and related balances (dollars in thousands):



	September 30, 2011				December 31, 2010					September 30, 2010
	Crude Oil Swaps/ Options		Natural Gas Swaps		Crude Oil Swaps/ Options			Natural Gas Swaps		Crude Oil Swaps/ Options			Natural Gas Swaps
Notional*	414,000		4,957,250		424,500			6,821,800		484,500			8,109,800
Maximum terms in years **	1.00		0.25		0.25			0.25		0.25			0.25
Derivative assets, current	$	1,885	$	6,937	$	248		$	7,675	$	466		$	8,816
Derivative assets, non-current	$	2,529	$	717	$	19		$	2,606	$	216		$	4,523
Derivative liabilities, current	$	—	$	—	$	3,814		$	—	$	3,224		$	—
Derivative liabilities, non-current	$	—	$	7	$	1,301		$	—	$	497		$	—
Pre-tax accumulated other comprehensive income (loss) included in Condensed Consolidated Balance Sheets	$	4,257	$	7,647	$	(5,313	)	$	10,281	$	(3,611	)	$	13,339
Earnings	$	157	$	—	$	465		$	—	$	572		$	—

____________

* Crude oil in Bbls, gas in MMBtus

** Refers to the term of the derivative instrument. Assets and liabilities are classified as current or non-current based on the timing of the hedged transaction and the corresponding settlement of the derivative instruments.

Based on September 30, 2011 market prices, an $8.3 million gain would be realized and reported in pre-tax earnings during the next 12 months related to hedges of production. Estimated and actual realized gains will likely change during the next 12 months as market prices fluctuate.

Gas Utilities - Gas Hedges

Our Gas Utilities segment distributes natural gas in four states. During the winter heating season, our gas customers are exposed to the effect of volatile natural gas prices; therefore, as allowed or required by state utility commissions, we have entered into certain exchange traded transactions, which may include natural gas futures, options and basis swaps, to reduce our customers' underlying exposure to these fluctuations. These transactions are considered derivatives in accordance with accounting standards for derivatives and mark-to-market adjustments are recorded as Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets. Gains and losses, as well as option premiums upon settlement, on these transactions are recorded as Regulatory assets or Regulatory liabilities in accordance with accounting standards for regulated operations. Accordingly, the earnings impact is recognized in the Condensed Consolidated Statements of Income as a component of PGA costs when the related costs are recovered through our rates as part of PGA costs in operating revenue.

The contract or notional amounts and terms of our natural gas derivative commodity instruments held at our Gas Utilities were as follows:



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in MMBtus)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Natural gas futures purchased	9,890,000	18	6,670,000	15	11,800,000	18
Natural gas options purchased	3,880,000	6	1,730,000	3	3,980,000	6
Natural gas basis swaps purchased	—	—	—	—	—	—

We had the following derivative balances related to the hedges in our gas utilities (in thousands):



	September 30, 2011			December 31, 2010			September 30, 2010
Current derivative assets	$	3,355		$	4,787		$	6,685
Non-current derivative assets	$	—		$	—		$	—
Non-current derivative liabilities	$	1,360		$	1,620		$	2,600
Net unrealized gain (loss) included in regulatory assets or regulatory liabilities	$	(11,813	)	$	(8,030	)	$	(18,381	)
Cash collateral receivable (payable) included in derivative assets/liabilities	$	12,058		$	10,355		$	20,519
Option premium included in Derivative assets, current	$	1,750		$	842		$	1,947

Financing Activities

We are exposed to interest rate risk associated with fluctuations in the interest rate on our variable interest rate debt. To manage this risk, we have entered into floating-to-fixed interest rate swap agreements with the intention to convert the debt's variable interest rate to a fixed rate.

Our interest rate swaps and related balances were as follows (dollars in thousands):



	September 30, 2011						December 31, 2010						September 30, 2010
	Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*			Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*			Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*
Current notional amount	$	150,000		$	250,000		$	150,000		$	250,000		$	150,000		$	250,000
Weighted average fixed interest rate	5.04		%	5.67		%	5.04		%	5.67		%	5.04		%	5.67		%
Maximum terms in years	5.25			0.25			6.00			1.00			6.25			0.25
Derivative liabilities, current	$	6,724		$	94,588		$	6,823		$	53,980		$	6,901		$	80,450
Derivative liabilities, non-current	$	21,108		$	—		$	14,976		$	—		$	21,518		$	—
Pre-tax accumulated other comprehensive loss included in Condensed Consolidated Balance Sheets	$	(27,832	)	$	—		$	(21,799	)	$	—		$	(28,419	)	$	—
Pre-tax (loss) gain included in Condensed Consolidated Statements of Income	$	—		$	(40,608	)	$	—		$	(15,193	)	$	—		$	(41,663	)
Cash collateral receivable (payable) included in accounts receivable	$	—		$	—		$	—		$	—		$	—		$	25,000

_____________


*	Maximum terms in years reflect the amended mandatory early termination dates. If the mandatory early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended annually, de-designated swaps totaling $100 million terminate in 7.25 years and de-designated swaps totaling $150 million terminate in 17.25 years.

Based on September 30, 2011 market interest rates and balances related to our designated interest rate swaps, a loss of approximately $6.7 million would be realized and reported in pre-tax earnings during the next 12 months. Estimated and realized losses will likely change during the next 12 months as market interest rates change. Note 13 provides further information related to the swaps that are not designated as hedges for accounting purposes.

Foreign Exchange Transactions

Our Energy Marketing segment conducts its marketing in the United States and Canada. Transactions in Canada are generally transacted in Canadian dollars and create exchange rate risk for us. To mitigate this risk, we enter into forward currency exchange contracts to offset earnings volatility from changes in exchange rates between the Canadian and United States dollar. Any balances that represent Canadian transactions are translated to United States dollars at the end of each accounting period at the exchange rate in effect at the balance sheet dates.

We had outstanding forward contracts included in Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets as follows (dollars in thousands):



	As of September 30, 2011			As of December 31, 2010			As of September 30, 2010
	Outstanding Notional Amounts		Latest Expiration (Months)	Outstanding Notional Amounts		Latest Expiration (Months)	Outstanding Notional Amounts		Latest Expiration (Months)
Canadian dollars purchased	$	—	—	$	15,000	1	$	5,000	1
Canadian dollars sold	$	—	—	$	—	—	$	—	—

Our outstanding foreign exchange contracts had a fair value as follows (in thousands):



	As of September 30, 2011		As of December 31, 2010			As of September 30, 2010
Fair Value of foreign exchange contracts	$	—	$	(143	)	$	(11	)

The table below includes gains (losses) recognized for foreign exchange contracts and foreign exchange re-measurement of assets and liabilities to our functional currency included in Operating revenue on the accompanying Condensed Consolidated Statements of Income (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Unrealized foreign exchange gain (loss)	$	783		$	97		$	621		$	181
Realized foreign exchange gain (loss)	$	(529	)	$	(61	)	$	(91	)	$	(652	)

- Definition

The entire disclosure for the entity's entire derivative instruments and hedging activities. Describes an entity's risk management strategies, derivatives in hedging activities and non-hedging derivative instruments, the assets, obligations, liabilities, revenues and expenses arising therefrom, and the amounts of and methodologies and assumptions used in determining the amounts of such items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 45
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Fair Value Measurements

9 Months Ended

Sep. 30, 2011

Fair Value Measurements [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Derivative Financial Instruments

Assets and liabilities carried at fair value are classified and disclosed in one of the following categories:

Level 1 — Unadjusted quoted prices available in active markets that are accessible at the measurement date for identical unrestricted assets or liabilities. This level primarily consists of financial instruments such as exchange-traded securities or listed derivatives.

Level 2 — Pricing inputs include quoted prices for identical or similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means.

Level 3 — Pricing inputs include significant inputs that are generally less observable from objective sources. These inputs reflect management's best estimate of fair value using its own assumptions about the assumptions a market participant would use in pricing the asset or liability.

Recurring Fair Value Measures

Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the placement within the fair value hierarchy levels.

The following tables set forth by level within the fair value hierarchy our assets and liabilities that were accounted for at fair value on a recurring basis (in thousands):



	As of September 30, 2011
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	370,586		$	9,193	$	(325,992	)	$	(3,268	)	$	50,519
Commodity derivatives — Oil and Gas	—		11,740			328		—			—			12,068
Commodity derivatives — Regulated Utilities Group	—		(8,703		)	—		—			12,058			3,355
Money market funds	9,006		—			—		—			—			9,006
Total	$	9,006	$	373,623		$	9,521	$	(325,992	)	$	8,790		$	74,948

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	365,646		$	4,619	$	(325,992	)	$	(12,294	)	$	31,979
Commodity derivatives — Oil and Gas	—		7			—		—			—			7
Commodity derivatives — Regulated Utilities Group	—		1,360			—		—			—			1,360
Foreign currency derivatives	—		—			—		—			—			—
Interest rate swaps	—		122,420			—		—			—			122,420
Total	$	—	$	489,433		$	4,619	$	(325,992	)	$	(12,294	)	$	155,766



	As of December 31, 2010
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	166,405		$	7,976	$	(122,639	)	$	(1,410	)	$	50,332
Commodity derivatives — Oil and Gas	—		10,281			266		—			—			10,547
Commodity derivatives — Regulated Utilities Group	—		(5,568		)	—		—			10,355			4,787
Money market funds	8,050		—			—		—			—			8,050
Foreign currency derivatives	—		166			—		—			—			166
Total	$	8,050	$	171,284		$	8,242	$	(122,639	)	$	8,945		$	73,882

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	143,537		$	2,463	$	(122,639	)	$	(5,368	)	$	17,993
Commodity derivatives — Oil and Gas			5,115			—		—			—			5,115
Commodity derivatives — Regulated Utilities Group	—		1,620			—		—			—			1,620
Foreign currency derivatives	—		21			—		—			—			21
Interest rate swaps	—		75,779			—		—			—			75,779
Total	$	—	$	226,072		$	2,463	$	(122,639	)	$	(5,368	)	$	100,528



	As of September 30, 2010
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	221,740		$	3,246	$	(154,306	)	$	(7,387	)	$	63,293
Commodity derivatives — Oil and Gas	—		13,459			562		—			—			14,021
Commodity derivatives — Regulated Utilities Group	—		(13,382		)	—		—			20,518			7,136
Money market funds	10,050		—			—		—			—			10,050
Foreign currency derivatives	—		—			—		—			—			—
Total	$	10,050	$	221,817		$	3,808	$	(154,306	)	$	13,131		$	94,500

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	172,401		$	840	$	(154,305	)	$	(22	)	$	18,914
Commodity derivatives — Oil and Gas	—		3,720			—		—			—			3,720
Commodity derivatives — Regulated Utilities Group	—		2,696			—		—			—			2,696
Foreign currency derivatives	—		11			—		—			—			11
Interest rate swaps	—		108,869			—		—			—			108,869
Total	$	—	$	287,697		$	840	$	(154,305	)	$	(22	)	$	134,210

The following tables present the changes in level 3 recurring fair value for the three and nine months ended September 30, 2011 and 2010, respectively (in thousands):



	Three Months Ended September 30, 2011			Nine Months Ended September 30, 2011
	Commodity Derivatives			Commodity Derivatives
Balance as of beginning of period	$	6,427		$	5,779
Unrealized losses	(4,359		)	(6,981		)
Unrealized gains	2,317			7,870
Purchases	—			—
Issuances	—			—
Settlements	197			(1,761		)
Transfers into level 3^(a)	254			—
Transfers out of level 3^(b)	66			(5		)
Balances at end of period	$	4,902		$	4,902

Changes in unrealized gains relating to instruments still held as of period-end	$	1,067		$	1,307



	Three Months Ended September 30, 2010			Nine Months Ended September 30, 2010
	Commodity Derivatives			Commodity Derivatives
Balance as of beginning of period	$	2,176		$	(556	)
Unrealized losses	961			(1,206		)
Unrealized gains	850			4,576
Settlements	(365		)	(1,170		)
Transfers into level 3^(a)	(62		)	(78		)
Transfers out of level 3^(b)	(592		)	1,402
Balances at end of period	$	2,968		$	2,968

Changes in unrealized losses relating to instruments still held as of period-end	$	(528	)	$	1,283

____________

(a) Transfers into level 3 represent assets and liabilities that were previously categorized as a higher level for which the inputs became unobservable.

(b) Transfers out of level 3 represent assets and liabilities that were previously classified as level 3 for which the lowest significant input became observable during the period.

Realized and unrealized gains (losses) for level 3 commodity derivatives totaling $(1.7) million and $1.3 million for the three and nine months ended September 30, 2011, respectively, are included in Operating revenue on the accompanying Condensed Consolidated Statements of Income while $(0.3) million and $(0.4) million was recorded through Accumulated other comprehensive income (loss) on the accompanying Condensed Consolidated Balance Sheets for the three and nine months ended September 30, 2011, respectively. Commodity derivatives classified as level 3 may be economically hedged as part of a total portfolio of instruments that may be classified in level 1 or 2, or with instruments that may not be accounted for at fair value. Accordingly, gains and losses associated with level 3 balances may not necessarily reflect trends occurring in the underlying business. Further, unrealized gains and losses for the period from level 3 items may be offset by unrealized gains and losses in positions classified in level 1 or 2, as well as positions that have been realized during the quarter.

Fair Value Measures

As required by accounting standards for derivatives and hedges, fair values within the following tables are presented on a gross basis and do not reflect the netting of asset and liability positions. Further, the amounts do not include net cash collateral of $21.1 million, $14.3 million and $13.2 million on deposit in margin accounts at September 30, 2011, December 31, 2010, and September 30, 2010, respectively, to collateralize certain financial instruments, which are included in Derivative assets - current, Derivative assets - non-current, Derivative liabilities - current and/or Derivative liabilities - non-current. Therefore, the gross balances are not indicative of either our actual credit exposure or net economic exposure. Additionally, the amounts below will not agree with the amounts presented on our Condensed Consolidated Balance Sheets, nor will they correspond to the fair value measurements presented in Note 12.

The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands):



As of September 30, 2011
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	198	$	2
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	2,474		738
Commodity derivatives	Derivative liabilities — non-current	—		—
Interest rate swaps	Derivative liabilities — current	—		6,724
Interest rate swaps	Derivative liabilities — non-current	—		21,108
Total derivatives designated as hedges		$	2,672	$	28,572

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	54,747	$	17,996
Commodity derivatives	Derivative assets — non-current	19,890		2,675
Commodity derivatives	Derivative liabilities — current	344,799		384,729
Commodity derivatives	Derivative liabilities — non-current	44,799		49,255
Foreign currency derivatives	Derivative liabilities — current	—		—
Interest rate swaps	Derivative liabilities — current	—		94,588
Total derivatives not designated as hedges		$	464,235	$	549,243



As of December 31, 2010
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	10,952	$	1,452
Commodity derivatives	Derivative assets — non-current	48		71
Commodity derivatives	Derivative liabilities — current	—		45
Commodity derivatives	Derivative liabilities — non-current	—		—
Interest rate swaps	Derivative liabilities — current	—		6,823
Interest rate swaps	Derivative liabilities — non-current	—		14,976
Total derivatives designated as hedges		$	11,000	$	23,367

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	149,936	$	113,364
Commodity derivatives	Derivative assets — non-current	12,382		3,099
Commodity derivatives	Derivative liabilities — current	20,588		42,865
Commodity derivatives	Derivative liabilities — non-current	978		7,363
Foreign currency derivatives	Derivative assets — current	166		21
Interest rate swaps	Derivative liabilities — current	—		53,980
Total derivatives not designated as hedges		$	184,050	$	220,692



As of September 30, 2010
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	20,387	$	1,329
Commodity derivatives	Derivative assets — non-current	11		—
Commodity derivatives	Derivative liabilities — current	—		219
Commodity derivatives	Derivative liabilities — non-current	—		3
Interest rate swaps	Derivative liabilities — current	—		6,901
Interest rate swaps	Derivative liabilities — non-current	—		21,519
Total derivatives designated as hedges		$	20,398	$	29,971

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	193,431	$	154,470
Commodity derivatives	Derivative assets — non-current	22,321		9,032
Commodity derivatives	Derivative liabilities — current	15,944		36,703
Commodity derivatives	Derivative liabilities — non-current	2,460		6,830
Interest rate swaps	Derivative liabilities — current	—		80,450
Interest rate swaps	Derivative liabilities — non-current	—		—
Foreign currency derivatives	Derivative asset — current	—		11
Foreign currency derivatives	Derivative liabilities — current	—		—
Total derivatives not designated as hedges		$	234,156	$	287,496

Our derivative activities are discussed in Note 12. The following tables present the impact that derivatives had on our Condensed Consolidated Statements of Income for the three and nine months ended September 30, 2011.

Fair Value Hedges

The impact of commodity contracts designated as fair value hedges and the related hedged items on our accompanying Condensed Consolidated Statements of Income was as follows (in thousands):



		Three Months Ended			Nine Months Ended
		September 30, 2011			September 30, 2011
Derivatives in Fair Value Hedging Relationships	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income

Commodity derivatives	Operating revenue	$	1,235		$	(7,502	)
Fair value adjustment for natural gas inventory designated as the hedged item	Operating revenue	(1,100		)	7,379
		$	135		$	(123	)



		Three Months Ended			Nine Months Ended
		September 30, 2010			September 30, 2010
Derivatives in Fair Value Hedging Relationships	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income

Commodity derivatives	Operating revenue	$	10,421		$	18,430
Fair value adjustment for natural gas inventory designated as the hedged item	Operating revenue	(10,247		)	(18,425		)
		$	174		$	5

Cash Flow Hedges

The impact of cash flow hedges on our Condensed Consolidated Statements of Income was as follows (in thousands):



Three Months Ended September 30, 2011
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	(6,958	)	Interest expense	$	(1,930	)		$	—
Commodity derivatives	10,095			Operating revenue	1,516			Operating revenue	—
Total	$	3,137			$	(414	)		$	—



Three Months Ended September 30, 2010
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	30,227		Interest expense	$	(1,859	)		$	—
Commodity derivatives	(24,912		)	Operating revenue	14,540			Operating revenue	(134		)
Total	$	5,315			$	12,681			$	(134	)



Nine Months Ended September 30, 2011
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	(11,428	)	Interest expense	$	(5,741	)		$	—
Commodity derivatives	9,784			Operating revenue	2,849			Operating revenue	—
Total	$	(1,644	)		$	(2,892	)		$	—



Nine Months Ended September 30, 2010
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	18,341		Interest expense	$	(5,683	)		$	—
Commodity derivatives	(18,822		)	Operating revenue	12,592			Operating revenue	(451		)
Total	$	(481	)		$	6,909			$	(451	)

Derivatives Not Designated as Hedge Instruments

The impact of derivative instruments that have not been designated as hedges on our Condensed Consolidated Statements of Income was as follows (in thousands):



		Three Months Ended			Nine Months Ended
		September 30, 2011			September 30, 2011
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income
Commodity derivatives	Operating revenue	$	(18,529	)	$	(14,321	)
Interest rate swaps - unrealized	Interest rate swaps — unrealized (loss) gain	(38,246		)	(40,608		)
Interest rate swaps - realized	Interest expense	(3,373		)	(10,077		)
Foreign currency contracts	Operating revenue	—			(143		)
		$	(60,148	)	$	(65,149	)



		Three Months Ended			Nine Months Ended
		September 30, 2010			September 30, 2010
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income
Commodity derivatives	Operating revenue	$	9,589		$	13,798
Interest rate swaps - unrealized	Interest rate swaps — unrealized (loss) gain	(13,710		)	(41,663		)
Interest rate swaps - realized	Interest expense	(3,773		)	(9,953		)
Foreign currency contracts	Operating revenue	3			(12		)
		$	(7,891	)	$	(37,830	)

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2011

Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]

Fair Value of Financial Instruments

FAIR VALUE OF FINANCIAL INSTRUMENTS

The estimated fair value of our financial instruments was as follows (in thousands):



	September 30, 2011				December 31, 2010				September 30, 2010
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents	$	74,779	$	74,779	$	32,438	$	32,438	$	58,975	$	58,975
Restricted cash	$	4,080	$	4,080	$	4,260	$	4,260	$	17,082	$	17,082
Derivative financial instruments - assets	$	65,942	$	65,942	$	65,832	$	65,832	$	84,450	$	84,450
Derivative financial instruments - liabilities	$	155,766	$	155,766	$	100,528	$	100,528	$	134,210	$	134,210
Notes payable	$	359,000	$	359,000	$	249,000	$	249,000	$	145,000	$	145,000
Long-term debt, including current maturities	$	1,285,087	$	1,430,271	$	1,191,231	$	1,290,519	$	1,193,607	$	1,303,338

The following methods and assumptions were used to estimate the fair value of each class of our financial instruments.

Cash, Cash Equivalents

The carrying amount approximates fair value due to the short maturity of these instruments.

Restricted Cash

The carrying amounts of our restricted cash approximate fair value due to the short maturity of these instruments.

Restricted cash is primarily related to cash held in escrow required by Black Hills Wyoming project financing agreements. These funds are held in 30-day guaranteed investment certificates of $1.2 million, $3.6 million and $10.6 million for September 30, 2011, December 31, 2010 and September 30, 2010, respectively.

At September 30, 2010, $6.2 million was held at our Oil and Gas segment in accordance with terms of a settlement.

Derivative Financial Instruments

Derivative financial instruments are carried at fair value. Our fair value measurements are developed using a variety of inputs by our risk management group, which is independent of the trading function. These inputs include unadjusted quoted prices where available; prices published by various third-party providers; and, when necessary, internally developed adjustments. In many cases, the internally developed prices are corroborated with external sources. Some of our transactions take place in markets with limited liquidity and limited price visibility. Additionally, descriptions of the various instruments we use and the valuation method employed are included in Notes 12 and 13.

Notes Payable

The carrying amount approximates fair value due to the variable interest rates with short reset periods.

Long-Term Debt

The fair value of our long-term debt is estimated based on quoted market rates for debt instruments having similar maturities and similar debt ratings. The first mortgage bonds issued by Black Hills Power and Cheyenne Light are either currently not callable or are subject to make-whole provisions which would eliminate any economic benefits if we were to call these bonds.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44A, 44B
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 15C, 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15A
-Subparagraph a-d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 3, 10, 14, 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ Details

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2011
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Legal Proceedings We are subject to various legal proceedings, claims and litigation as described in Note 19 of the Notes to our Consolidated Financial Statements in our 2010 Annual Report on Form 10-K. There are no material proceedings that have developed, no material developments with respect to existing legal proceedings and no material proceedings have terminated during the first nine months of 2011. In the normal course of business, we are subject to various lawsuits, actions, proceedings, claims and other matters asserted under laws and regulations. We believe the amounts provided in our consolidated financial statements are adequate in light of the probable and estimable contingencies. However, there can be no assurance that the actual amounts required to satisfy alleged liabilities from various legal proceedings, claims and other matters discussed below, and to comply with applicable laws and regulations, will not exceed the amounts reflected in our consolidated financial statements. As such, costs, if any, that may be incurred in excess of those amounts provided as of September 30, 2011 cannot be reasonably determined and could have a material effect on our results of operations or financial position. Other Commitments Construction of a 180 MW power generation facility by our Colorado Electric utility and a 200 MW power generation facility by our Power Generation segment is progressing. Total cost of construction is expected to be approximately $227.0 million for Colorado Electric and approximately $260.0 million for the Power Generation segment. Construction is expected to be completed at both facilities by December 31, 2011. We have procured contracts for the turbines, building construction and labor. As of September 30, 2011, we have committed contracts for 100% of the construction for the Colorado Electric utility and 100% of the construction for the Power Generation segment. PPA Extension In June 2011, FERC approved an extension of the PPA between Black Hills Wyoming and Cheyenne Light which was due to expire in August 2011. This agreement, now extended through August 2014, provides energy and capacity to Cheyenne Light from Black Hills Wyoming's Gillette CT.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 14
-Paragraph 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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+ Details

Guarantees	9 Months Ended
Guarantees	Sep. 30, 2011
Guarantees [Abstract]
Guarantees [Text Block]	GUARANTEES We had provided a guarantee for up to $7.0 million of Enserco's obligations under an agency agreement. During the first quarter of 2011, the guarantee expired upon fulfillment of all obligations under the contract. The construction of the office building in Papillion, Nebraska was completed and the guarantee for $6.0 million was terminated upon purchase of the building on April 1, 2011. In June 2011, a guarantee to Colorado Interstate Gas was amended. It was amended to increase the guarantee amount to $10.0 million and extend the expiration date to July 31, 2012. All other terms remained the same. In June 2011, we issued a guarantee to Cross Timbers Energy Services for the performance and payment obligations of Black Hills Utility Holdings for natural gas supply purchases up to $7.5 million. The guarantee expires on June 30, 2012 or upon 30 days written notice to the counterparty. In July 2011, we issued a $33.3 million guarantee to Vestas-American Wind Technology, Inc. for the performance and payment obligations of Colorado Electric relating to the purchase of wind turbines for a Colorado Electric wind power generation project. This guarantee will remain in effect until satisfaction of Colorado Electric's contractual obligations. We expect the guarantee to expire on or about January 15, 2013.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2011
Subsequent Events [Abstract]
Subsequent Event	SUBSEQUENT EVENT Equity Forward Instrument On November 1, 2011, we settled the equity forward agreements by physically delivering 4,413,519 shares of common stock and we received cash proceeds of approximately $120 million The price used to determine cash proceeds was calculated based on the November 2010 public offering price of our common stock, adjusted for underwriting fees, as well as a daily adjustment based on the federal funds rate less a spread, and a decrease to reflect the dividend paid on our common stock subsequent to November 10, 2010.

Supplemental Disclosure of Cash Flow Information (Tables)

9 Months Ended

Sep. 30, 2011

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosure of Cash Flow Information



	Nine Months Ended
	September 30, 2011			September 30, 2010
	(in thousands)
Non-cash investing activities—
Property, plant and equipment acquired with accrued liabilities	$	49,566		$	37,661
Cash (paid) refunded during the period for—
Interest (net of amounts capitalized)	$	(61,461	)	$	(62,740	)
Income taxes, net	$	11,826		$	(488	)

Materials, Supplies and Fuel (Tables)

9 Months Ended

Sep. 30, 2011

Inventory, Net [Abstract]

Schedule of Inventory, current



	September 30, 2011		December 31, 2010		September 30, 2010
Materials and supplies	$	37,611	$	31,749	$	31,192
Fuel - Electric Utilities	8,639		9,687		9,056
Natural gas in storage — Gas Utilities	38,641		21,691		36,782
Commodities held by Energy Marketing*	49,572		76,550		68,221
Total materials, supplies and fuel	$	134,463	$	139,677	$	145,251

_____________

Accounts Receivable (Tables)

9 Months Ended

Sep. 30, 2011

Receivables [Abstract]

Summary of receivables

Following is a summary of receivables (in thousands):



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
September 30, 2011	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	41,889	$	16,401	$	58,290	$	(590	)	$	57,700
Gas	21,168		12,518		33,686		(789		)	32,897
Oil and Gas	8,820		—		8,820		(161		)	8,659
Coal Mining	1,845		—		1,845		—			1,845
Energy Marketing	139,332		—		139,332		(174		)	139,158
Power Generation	119		—		119		—			119
Corporate	1,453		—		1,453		—			1,453
Total	$	214,626	$	28,919	$	243,545	$	(1,714	)	$	241,831



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
December 31, 2010	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	51,005	$	19,572	$	70,577	$	(708	)	$	69,869
Gas	41,970		40,376		82,346		(1,425		)	80,921
Oil and Gas	6,213		—		6,213		(161		)	6,052
Coal Mining	2,420		—		2,420		—			2,420
Energy Marketing	157,064		—		157,064		(69		)	156,995
Power Generation	307		—		307		—			307
Corporate (a)	12,247		—		12,247		—			12,247
Total	$	271,226	$	59,948	$	331,174	$	(2,363	)	$	328,811



As of	Accounts		Unbilled		Total Accounts		Less Allowance for			Accounts
September 30, 2010	Receivable, Trade		Revenue		Receivable		Doubtful Accounts			Receivable, net
Electric	$	41,955	$	17,959	$	59,914	$	(927	)	$	58,987
Gas	19,611		11,107		30,718		(830		)	29,888
Oil and Gas	6,112		—		6,112		(161		)	5,951
Coal Mining	2,201		—		2,201		—			2,201
Energy Marketing	99,850		—		99,850		(375		)	99,475
Power Generation	463		—		463		—			463
Corporate ^{(a) (b)}	37,515		—		37,515		—			37,515
Total	$	207,707	$	29,066	$	236,773	$	(2,293	)	$	234,480

(a) During the third quarter of 2010 we reached a settlement with the IRS and received a refund relating to this settlement during 2011 of $12.0 million, excluding interest income.

(b) includes cash collateral receivable on de-designated interest rate swaps. See Note 12 for further information.

Notes Payable (Tables)

9 Months Ended

Sep. 30, 2011

Line of Credit Facility

Schedule of Short-term Debt

We had the following short-term debt issued and outstanding as of the Condensed Consolidated Balance Sheet dates (in thousands):



	As of September 30, 2011				As of December 31, 2010				As of September 30, 2010
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	209,000	$	42,355	$	149,000	$	46,900	$	145,000	$	15,500
Enserco Credit Facility	—		132,625		—		166,900		—		131,500
Term Loan due 2011	—		—		100,000		—		—		—
Term Loan due 2012	150,000		—		—		—		—		—
Total	$	359,000	$	174,980	$	249,000	$	213,800	$	145,000	$	147,000

Revolving Credit Facility [Member]

Line of Credit Facility

Deferred Financing Costs



	Deferred Financing	Amortization Expense
	Costs Remaining on Balance Sheet as of	Three Months Ended September 30,				Nine Months Ended September 30,
	September 30, 2011	2011		2010		2011		2010
Deferred Financing Costs - Revolving Credit Facility	$1,970	$	473	$	481	$	1,419	$	866

Credit Facility Covenants



As of September 30, 2011	Actual			Covenant Requirement
Consolidated Net Worth	$	1,088,000		$	871,300
Recourse Leverage Ratio	61.3		%	65.0		%

Enserco Credit Facility

Line of Credit Facility

Deferred Financing Costs



		Amortization Expense
	Deferred Financing Costs Remaining on Balance Sheet as of	Three Months Ended September 30,				Nine Months Ended September 30,
	September 30, 2011	2011		2010		2011		2010
Deferred Financing Costs - Enserco Credit Facility	$812	$	305	$	263	$	866	$	1,245

Earnings per Share (Tables)

9 Months Ended

Sep. 30, 2011

Earnings Per Share [Abstract]

Earnings Per Share Reconciliation

A reconciliation of share amounts used to compute earnings (loss) per share is as follows (in thousands):



	Three Months Ended September 30,					Nine Months Ended September 30,
	2011			2010		2011		2010

Net income (loss)	$	(10,525	)	$	12,390	$	24,137	$	35,165

Weighted average shares - basic	39,145			38,933		39,105		38,895
Dilutive effect of:
Restricted stock	—			131		147		110
Stock options	—			12		16		9
Forward equity issuance	—			—		473		—
Other	—			57		51		38
Weighted average shares - diluted	39,145			39,133		39,792		39,052

Antidilutive Securities Excluded from Computation of Earnings Per Share



	Three Months Ended September 30,		Nine Months Ended September 30,
	2011	2010	2011	2010
Stock options	176	128	119	169
Restricted stock	20	2	17	2
Other stock	27	1	19	1
Anti-dilutive shares	223	131	155	172

Comprehensive Income (Loss) (Tables)

9 Months Ended

Sep. 30, 2011

Other Comprehensive (Loss) Income [Abstract]

Components of Comprehensive Income (loss)

The following table presents the components of our comprehensive income (loss) (in thousands):



	Three Months Ended September 30, 2011
Net income (loss)				$	(10,525	)
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	3,137
Taxes on fair value adjustment on derivatives designated as cash flow hedges	(1,215		)
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,922

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	414
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	(129		)
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				285

Comprehensive income (loss)				$	(8,318	)



	Three Months Ended September 30, 2010
Net income (loss)				$	12,390
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	517
Taxes on fair value adjustment on derivatives designated as cash flow hedges	486
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,003

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	(4,730	)
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	1,761
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				(2,969		)

Comprehensive income (loss)				$	10,424



	Nine Months Ended September 30, 2011
Net income (loss)				$	24,137
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	—
Taxes on benefit plan liability adjustments	—
Benefit plan liability adjustments, net of tax				—

Fair value adjustment on derivatives designated as cash flow hedges	$	(1,644	)
Taxes on fair value adjustment on derivatives designated as cash flow hedges	653
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				(991		)

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	2,892
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	(985		)
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				1,907

Comprehensive income (loss)				$	25,053



	Nine Months Ended September 30, 2010
Net income (loss)				$	35,165
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	$	(8	)
Taxes on benefit plan liability adjustments	(7		)
Benefit plan liability adjustments, net of tax				(15		)

Fair value adjustment on derivatives designated as cash flow hedges	$	495
Taxes on fair value adjustment on derivatives designated as cash flow hedges	641
Fair value adjustment on derivatives designated as cash flow hedges, net of tax				1,136

Reclassification adjustments on cash flow hedges settled and included in net income (loss)	$	(6,909	)
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	2,543
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax				(4,366		)

Comprehensive income (loss)				$	31,920

Balances by classification included within Accumulated Other Comprehensive Income (Loss)

Balances by classification included within Accumulated other comprehensive income (loss) on the accompanying Condensed Consolidated Balance Sheets are as follows (in thousands):



	September 30, 2011			December 31, 2010			September 30, 2010
Derivatives designated as cash flow hedges	$	(11,523	)	$	(12,437	)	$	(12,741	)
Benefit plans	(11,142		)	(11,142		)	(9,636		)
Amount from equity-method investees	—			(2		)	(32		)
Total	$	(22,665	)	$	(23,581	)	$	(22,409	)

Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2011

Defined Benefit Plan Disclosure [Line Items]

Contributions to Healthcare and Supplemental Plans

Contributions to the Healthcare Plans and the Supplemental Plans expected to be made in the form of benefit payments are as follows (in thousands):



	Contributions Made		Contributions Made
	Three Months Ended September 30, 2011		Nine Months Ended September 30, 2011		Contributions Remaining for 2011		Contributions Anticipated for 2012
Defined Benefit Pension Plans	$	10,500	$	11,050	$	—	$	7,869
Non-pension Defined Benefit Postretirement Healthcare Plans	$	882	$	2,646	$	882	$	3,765
Supplemental Non-qualified Defined Benefit Plans	$	235	$	705	$	236	$	896

Pension Plans, Defined Benefit

Defined Benefit Plan Disclosure [Line Items]

Components of net periodic benefit cost

The components of net periodic benefit cost for the Pension Plans were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Service cost	$	1,355		$	1,533		$	4,066		$	4,599
Interest cost	3,732			3,773			11,196			11,319
Expected return on plan assets	(4,239		)	(3,623		)	(12,717		)	(10,869		)
Prior service cost	25			305			75			915
Net loss (gain)	1,135			500			3,405			1,500
Curtailment expense	—			—			—			—
Net periodic benefit cost	$	2,008		$	2,488		$	6,025		$	7,464

Non-pension Postretirement Healthcare Plans, Defined Benefit

Defined Benefit Plan Disclosure [Line Items]

Components of net periodic benefit cost

The components of net periodic benefit cost for the Healthcare Plans were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Service cost	$	375		$	377		$	1,125		$	1,131
Interest cost	542			611			1,626			1,833
Expected return on plan assets	(41		)	(52		)	(123		)	(156		)
Prior service benefit	(120		)	(77		)	(360		)	(231		)
Net transition obligation	—			—			—			—
Net loss (gain)	169			159			507			477
Net periodic benefit cost	$	925		$	1,018		$	2,775		$	3,054

Supplemental Non-qualified Plans, Defined Benefit

Defined Benefit Plan Disclosure [Line Items]

Components of net periodic benefit cost

The components of net periodic benefit cost for the Supplemental Plans were as follows (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2011		2010		2011		2010
Service cost	$	257	$	171	$	771	$	513
Interest cost	324		321		973		963
Prior service cost	1		1		3		3
Net loss (gain)	128		71		383		213
Net periodic benefit cost	$	710	$	564	$	2,130	$	1,692

Summary of Information Relating to Segments of our Business (Tables)

9 Months Ended

Sep. 30, 2011

Segment Reporting Information, Additional Information [Abstract]

Segment information included in Condensed Consolidated Statements of Income



Three Months Ended September 30, 2011	External Operating Revenue		Inter-segment Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	151,063	$	2,653		$	15,790
Gas	72,651		—			572
Non-regulated Energy:
Oil and Gas	19,163		—			241
Power Generation	1,011		7,089			337
Coal Mining	9,184		8,651			555
Energy Marketing	3,388		3,550			273
Corporate ^(a)	—		—			(27,943		)
Inter-segment eliminations	—		(21,943		)	(350		)
Total	$	256,460	$	—		$	(10,525	)



Three Months Ended September 30, 2010	External Operating Revenue		Inter-segment Operating Revenue ^(d)			Net Income (Loss)
Utilities:
Electric ^(b)	$	138,761	$	2,884		$	18,537
Gas ^(c)	72,323		—			(595		)
Non-regulated Energy:
Oil and Gas ^(e)	19,354		—			836
Power Generation	1,124		6,731			575
Coal Mining	7,744		6,533			1,673
Energy Marketing	9,060		(87		)	1,370
Corporate ^{(a) (f)}	—		—			(10,093		)
Inter-segment eliminations	—		(14,933		)	87
Total	$	248,366	$	1,128		$	12,390



Nine Months Ended September 30, 2011	External Operating Revenue		Inter-segment Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	431,624	$	9,902		$	34,653
Gas	402,839		—			24,275
Non-regulated Energy:
Oil and Gas	55,907		—			(553		)
Power Generation	2,750		20,750			2,071
Coal Mining	23,064		25,806			(1,124		)
Energy Marketing	16,701		5,178			1,327
Corporate ^(a)	—		—			(36,101		)
Inter-segment eliminations	—		(61,636		)	(411		)
Total	$	932,885	$	—		$	24,137



Nine Months Ended September 30, 2010	External Operating Revenue		Inter-segment Operating Revenue ^(d)			Net Income (Loss)
Utilities:
Electric^(b)	$	415,092	$	11,627		$	35,585
Gas ^(c)	402,608		—			18,017
Non-regulated Energy:
Oil and Gas ^(e)	57,755		—			3,405
Power Generation	3,266		19,336			1,239
Coal Mining	22,431		20,875			6,093
Energy Marketing	27,797		(157		)	4,890
Corporate ^{(a) (f)}	—		—			(34,221		)
Inter-segment eliminations	—		(48,298		)	157
Total	$	928,949	$	3,383		$	35,165

____________

(b) Net income (loss) includes a $4.1 million after-tax gain on sale of a 23% interest in Wygen III to the City of Gillette.

(c) Net income (loss) includes a $1.7 million after-tax gain on sale of operating assets in the Gas Utilities at Nebraska Gas.

(d) Total operating revenue has been restated to reflect elimination of intercompany activities previously not eliminated. See Note 1 for further information.

(e) Net income (loss) includes a $0.4 million reduction of income taxes as a result of a re-measurement of a previously reported uncertain tax position due to a settlement with the IRS.

Segment information included in Condensed Consolidated Balance Sheets



Total assets	September 30, 2011		December 31, 2010		September 30, 2010
Utilities:
Electric ^(a)	$	1,917,183	$	1,834,019	$	1,771,014
Gas	683,163		722,287		659,801
Non-regulated Energy:
Oil and Gas	405,513		349,991		358,113
Power Generation^(a)	372,313		293,334		249,778
Coal Mining	94,908		96,962		94,149
Energy Marketing	340,499		314,930		287,173
Corporate	139,788		99,986		120,209
Total assets	$	3,953,367	$	3,711,509	$	3,540,237

____________

- Definition

Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

+ References + Details

Risk Management Activities (Tables)

9 Months Ended

Sep. 30, 2011

Financing Activities

Derivative [Line Items]

Interest rate swaps and related balances

Our interest rate swaps and related balances were as follows (dollars in thousands):



	September 30, 2011						December 31, 2010						September 30, 2010
	Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*			Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*			Designated Interest Rate Swaps			Dedesignated Interest Rate Swaps*
Current notional amount	$	150,000		$	250,000		$	150,000		$	250,000		$	150,000		$	250,000
Weighted average fixed interest rate	5.04		%	5.67		%	5.04		%	5.67		%	5.04		%	5.67		%
Maximum terms in years	5.25			0.25			6.00			1.00			6.25			0.25
Derivative liabilities, current	$	6,724		$	94,588		$	6,823		$	53,980		$	6,901		$	80,450
Derivative liabilities, non-current	$	21,108		$	—		$	14,976		$	—		$	21,518		$	—
Pre-tax accumulated other comprehensive loss included in Condensed Consolidated Balance Sheets	$	(27,832	)	$	—		$	(21,799	)	$	—		$	(28,419	)	$	—
Pre-tax (loss) gain included in Condensed Consolidated Statements of Income	$	—		$	(40,608	)	$	—		$	(15,193	)	$	—		$	(41,663	)
Cash collateral receivable (payable) included in accounts receivable	$	—		$	—		$	—		$	—		$	—		$	25,000

_____________


*	Maximum terms in years reflect the amended mandatory early termination dates. If the mandatory early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended annually, de-designated swaps totaling $100 million terminate in 7.25 years and de-designated swaps totaling $150 million terminate in 17.25 years.

Foreign Exchange Contracts

Derivative [Line Items]

Gains and losses recognized in Operating revenue



	Three Months Ended September 30,						Nine Months Ended September 30,
	2011			2010			2011			2010
Unrealized foreign exchange gain (loss)	$	783		$	97		$	621		$	181
Realized foreign exchange gain (loss)	$	(529	)	$	(61	)	$	(91	)	$	(652	)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing

Derivative [Line Items]

Contract or notional amounts and terms of marketing activities and derivative commodity instruments

The contract or notional amounts and terms of our marketing activities and derivative commodity instruments were as follows:



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of MMBtus)
Natural gas basis swaps purchased	425,360	42	399,128	22	335,805	25
Natural gas basis swaps sold	443,489	42	426,903	22	358,929	25
Natural gas fixed-for-float swaps purchased	251,602	27	135,005	33	84,636	36
Natural gas fixed-for-float swaps sold	249,808	27	150,803	22	97,210	18
Natural gas physical purchases	105,446	27	144,948	36	135,818	18
Natural gas physical sales	122,232	72	143,021	36	136,530	36
Natural gas futures purchased	78,100	7	—	—	—	—
Natural gas futures sold	96,730	7	—	—	—	—
Natural gas options purchased	6,000	2	—	—	—	—
Natural gas options sold	6,000	2	—	—	—	—



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of Bbls)
Crude oil physical purchases	7,326	15	5,628	16	5,561	15
Crude oil physical sales	7,917	15	6,921	16	4,759	15
Crude oil fixed-for-float swaps purchased	—	—	20	3	135	1
Crude oil fixed-for-float swaps sold	10	2	240	4	289	3



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
(notional in thousands of tons)
Coal fixed-for-float swaps purchased	8,305	27	4,060	36	5,585	39
Coal fixed-for-float swaps sold	9,710	27	3,720	36	4,445	39
Coal physical purchases	27,982	39	24,634	48	24,100	51
Coal physical sales	13,331	39	9,046	36	6,213	35
Coal options purchased	4,530	51	2,835	48	1,980	27
Coal options sold	572	6	270	12	360	15



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in thousands of MWh):	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Power physical purchases	153	54	—	—	—	—
Power physical sales	153	54	—	—	—	—
Power fixed-for-float swaps purchased	12,370	27	—	—	—	—
Power fixed-for-float swaps sold	12,439	27	—	—	—	—



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in thousands of MWh):	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Environmental products physical purchases	283	54	—	—	—	—
Environmental products physical sales	273	54	—	—	—	—

Fair value hedging instruments included in financial statements



	September 30, 2011			December 31, 2010			September 30, 2010
Current derivative assets	$	36,550		$	43,862		$	55,366
Non-current derivative assets	$	13,969		$	6,635		$	8,023
Current derivative liabilities	$	27,851		$	14,550		$	17,743
Non-current derivative liabilities	$	4,128		$	3,464		$	1,277
Cash collateral receivable (payable) included in derivative assets/liabilities	$	9,026		$	3,958		$	(7,365	)
Unrealized gains	$	9,514		$	28,525		$	51,734
Net derivative assets (liabilities) with credit risk-related contingent features that require Enserco to maintain a specific credit rating	$	—		$	—		$	—
Cash collateral receivable included in Other current assets	$	34,642		$	9,919		$	1,854
Cash collateral (payable) included in Other current liabilities	$	(802	)	$	(1,079	)	$	(1,079	)

Energy Marketing [Member] | Foreign Exchange Contracts

Derivative [Line Items]

Foreign exchange contracts included in Condensed Consolidated Balance Sheets

We had outstanding forward contracts included in Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets as follows (dollars in thousands):



	As of September 30, 2011			As of December 31, 2010			As of September 30, 2010
	Outstanding Notional Amounts		Latest Expiration (Months)	Outstanding Notional Amounts		Latest Expiration (Months)	Outstanding Notional Amounts		Latest Expiration (Months)
Canadian dollars purchased	$	—	—	$	15,000	1	$	5,000	1
Canadian dollars sold	$	—	—	$	—	—	$	—	—

Our outstanding foreign exchange contracts had a fair value as follows (in thousands):



	As of September 30, 2011		As of December 31, 2010			As of September 30, 2010
Fair Value of foreign exchange contracts	$	—	$	(143	)	$	(11	)

Oil and Gas [Member] | Oil and Gas Exploration and Production

Derivative [Line Items]

Cash flow heding instruments included in financial statements

We had the following derivatives and related balances (dollars in thousands):



	September 30, 2011				December 31, 2010					September 30, 2010
	Crude Oil Swaps/ Options		Natural Gas Swaps		Crude Oil Swaps/ Options			Natural Gas Swaps		Crude Oil Swaps/ Options			Natural Gas Swaps
Notional*	414,000		4,957,250		424,500			6,821,800		484,500			8,109,800
Maximum terms in years **	1.00		0.25		0.25			0.25		0.25			0.25
Derivative assets, current	$	1,885	$	6,937	$	248		$	7,675	$	466		$	8,816
Derivative assets, non-current	$	2,529	$	717	$	19		$	2,606	$	216		$	4,523
Derivative liabilities, current	$	—	$	—	$	3,814		$	—	$	3,224		$	—
Derivative liabilities, non-current	$	—	$	7	$	1,301		$	—	$	497		$	—
Pre-tax accumulated other comprehensive income (loss) included in Condensed Consolidated Balance Sheets	$	4,257	$	7,647	$	(5,313	)	$	10,281	$	(3,611	)	$	13,339
Earnings	$	157	$	—	$	465		$	—	$	572		$	—

____________

* Crude oil in Bbls, gas in MMBtus

Gas Utilities [Member] | Regulated Gas Utilities - Gas Hedges

Derivative [Line Items]

Contract or notional amounts and terms of marketing activities and derivative commodity instruments

The contract or notional amounts and terms of our natural gas derivative commodity instruments held at our Gas Utilities were as follows:



	Outstanding at		Outstanding at		Outstanding at
	September 30, 2011		December 31, 2010		September 30, 2010
(notional in MMBtus)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)	Notional Amounts	Latest Expiration (months)
Natural gas futures purchased	9,890,000	18	6,670,000	15	11,800,000	18
Natural gas options purchased	3,880,000	6	1,730,000	3	3,980,000	6
Natural gas basis swaps purchased	—	—	—	—	—	—

Cash flow heding instruments included in financial statements

We had the following derivative balances related to the hedges in our gas utilities (in thousands):



	September 30, 2011			December 31, 2010			September 30, 2010
Current derivative assets	$	3,355		$	4,787		$	6,685
Non-current derivative assets	$	—		$	—		$	—
Non-current derivative liabilities	$	1,360		$	1,620		$	2,600
Net unrealized gain (loss) included in regulatory assets or regulatory liabilities	$	(11,813	)	$	(8,030	)	$	(18,381	)
Cash collateral receivable (payable) included in derivative assets/liabilities	$	12,058		$	10,355		$	20,519
Option premium included in Derivative assets, current	$	1,750		$	842		$	1,947

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2011

Derivative Instruments, Gain (Loss)

Fair value assets and liabilities measured on recurring basis

The following tables set forth by level within the fair value hierarchy our assets and liabilities that were accounted for at fair value on a recurring basis (in thousands):



	As of September 30, 2011
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	370,586		$	9,193	$	(325,992	)	$	(3,268	)	$	50,519
Commodity derivatives — Oil and Gas	—		11,740			328		—			—			12,068
Commodity derivatives — Regulated Utilities Group	—		(8,703		)	—		—			12,058			3,355
Money market funds	9,006		—			—		—			—			9,006
Total	$	9,006	$	373,623		$	9,521	$	(325,992	)	$	8,790		$	74,948

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	365,646		$	4,619	$	(325,992	)	$	(12,294	)	$	31,979
Commodity derivatives — Oil and Gas	—		7			—		—			—			7
Commodity derivatives — Regulated Utilities Group	—		1,360			—		—			—			1,360
Foreign currency derivatives	—		—			—		—			—			—
Interest rate swaps	—		122,420			—		—			—			122,420
Total	$	—	$	489,433		$	4,619	$	(325,992	)	$	(12,294	)	$	155,766



	As of December 31, 2010
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	166,405		$	7,976	$	(122,639	)	$	(1,410	)	$	50,332
Commodity derivatives — Oil and Gas	—		10,281			266		—			—			10,547
Commodity derivatives — Regulated Utilities Group	—		(5,568		)	—		—			10,355			4,787
Money market funds	8,050		—			—		—			—			8,050
Foreign currency derivatives	—		166			—		—			—			166
Total	$	8,050	$	171,284		$	8,242	$	(122,639	)	$	8,945		$	73,882

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	143,537		$	2,463	$	(122,639	)	$	(5,368	)	$	17,993
Commodity derivatives — Oil and Gas			5,115			—		—			—			5,115
Commodity derivatives — Regulated Utilities Group	—		1,620			—		—			—			1,620
Foreign currency derivatives	—		21			—		—			—			21
Interest rate swaps	—		75,779			—		—			—			75,779
Total	$	—	$	226,072		$	2,463	$	(122,639	)	$	(5,368	)	$	100,528



	As of September 30, 2010
	Level 1		Level 2			Level 3		Counterparty Netting			Cash Collateral			Total
Assets:
Commodity derivatives — Energy Marketing	$	—	$	221,740		$	3,246	$	(154,306	)	$	(7,387	)	$	63,293
Commodity derivatives — Oil and Gas	—		13,459			562		—			—			14,021
Commodity derivatives — Regulated Utilities Group	—		(13,382		)	—		—			20,518			7,136
Money market funds	10,050		—			—		—			—			10,050
Foreign currency derivatives	—		—			—		—			—			—
Total	$	10,050	$	221,817		$	3,808	$	(154,306	)	$	13,131		$	94,500

Liabilities:
Commodity derivatives — Energy Marketing	$	—	$	172,401		$	840	$	(154,305	)	$	(22	)	$	18,914
Commodity derivatives — Oil and Gas	—		3,720			—		—			—			3,720
Commodity derivatives — Regulated Utilities Group	—		2,696			—		—			—			2,696
Foreign currency derivatives	—		11			—		—			—			11
Interest rate swaps	—		108,869			—		—			—			108,869
Total	$	—	$	287,697		$	840	$	(154,305	)	$	(22	)	$	134,210

Changes in level 3 recurring fair value

The following tables present the changes in level 3 recurring fair value for the three and nine months ended September 30, 2011 and 2010, respectively (in thousands):



	Three Months Ended September 30, 2011			Nine Months Ended September 30, 2011
	Commodity Derivatives			Commodity Derivatives
Balance as of beginning of period	$	6,427		$	5,779
Unrealized losses	(4,359		)	(6,981		)
Unrealized gains	2,317			7,870
Purchases	—			—
Issuances	—			—
Settlements	197			(1,761		)
Transfers into level 3^(a)	254			—
Transfers out of level 3^(b)	66			(5		)
Balances at end of period	$	4,902		$	4,902

Changes in unrealized gains relating to instruments still held as of period-end	$	1,067		$	1,307



	Three Months Ended September 30, 2010			Nine Months Ended September 30, 2010
	Commodity Derivatives			Commodity Derivatives
Balance as of beginning of period	$	2,176		$	(556	)
Unrealized losses	961			(1,206		)
Unrealized gains	850			4,576
Settlements	(365		)	(1,170		)
Transfers into level 3^(a)	(62		)	(78		)
Transfers out of level 3^(b)	(592		)	1,402
Balances at end of period	$	2,968		$	2,968

Changes in unrealized losses relating to instruments still held as of period-end	$	(528	)	$	1,283

____________

(a) Transfers into level 3 represent assets and liabilities that were previously categorized as a higher level for which the inputs became unobservable.

(b) Transfers out of level 3 represent assets and liabilities that were previously classified as level 3 for which the lowest significant input became observable during the period.

Fair Value Hedging

Derivative Instruments, Gain (Loss)

Fair value and balance sheet classification of derivative instruments

The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands):



As of September 30, 2011
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	198	$	2
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	2,474		738
Commodity derivatives	Derivative liabilities — non-current	—		—
Interest rate swaps	Derivative liabilities — current	—		6,724
Interest rate swaps	Derivative liabilities — non-current	—		21,108
Total derivatives designated as hedges		$	2,672	$	28,572

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	54,747	$	17,996
Commodity derivatives	Derivative assets — non-current	19,890		2,675
Commodity derivatives	Derivative liabilities — current	344,799		384,729
Commodity derivatives	Derivative liabilities — non-current	44,799		49,255
Foreign currency derivatives	Derivative liabilities — current	—		—
Interest rate swaps	Derivative liabilities — current	—		94,588
Total derivatives not designated as hedges		$	464,235	$	549,243



As of December 31, 2010
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	10,952	$	1,452
Commodity derivatives	Derivative assets — non-current	48		71
Commodity derivatives	Derivative liabilities — current	—		45
Commodity derivatives	Derivative liabilities — non-current	—		—
Interest rate swaps	Derivative liabilities — current	—		6,823
Interest rate swaps	Derivative liabilities — non-current	—		14,976
Total derivatives designated as hedges		$	11,000	$	23,367

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	149,936	$	113,364
Commodity derivatives	Derivative assets — non-current	12,382		3,099
Commodity derivatives	Derivative liabilities — current	20,588		42,865
Commodity derivatives	Derivative liabilities — non-current	978		7,363
Foreign currency derivatives	Derivative assets — current	166		21
Interest rate swaps	Derivative liabilities — current	—		53,980
Total derivatives not designated as hedges		$	184,050	$	220,692



As of September 30, 2010
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	20,387	$	1,329
Commodity derivatives	Derivative assets — non-current	11		—
Commodity derivatives	Derivative liabilities — current	—		219
Commodity derivatives	Derivative liabilities — non-current	—		3
Interest rate swaps	Derivative liabilities — current	—		6,901
Interest rate swaps	Derivative liabilities — non-current	—		21,519
Total derivatives designated as hedges		$	20,398	$	29,971

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	193,431	$	154,470
Commodity derivatives	Derivative assets — non-current	22,321		9,032
Commodity derivatives	Derivative liabilities — current	15,944		36,703
Commodity derivatives	Derivative liabilities — non-current	2,460		6,830
Interest rate swaps	Derivative liabilities — current	—		80,450
Interest rate swaps	Derivative liabilities — non-current	—		—
Foreign currency derivatives	Derivative asset — current	—		11
Foreign currency derivatives	Derivative liabilities — current	—		—
Total derivatives not designated as hedges		$	234,156	$	287,496

Gains and losses recognized in income



		Three Months Ended			Nine Months Ended
		September 30, 2011			September 30, 2011
Derivatives in Fair Value Hedging Relationships	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income

Commodity derivatives	Operating revenue	$	1,235		$	(7,502	)
Fair value adjustment for natural gas inventory designated as the hedged item	Operating revenue	(1,100		)	7,379
		$	135		$	(123	)



		Three Months Ended			Nine Months Ended
		September 30, 2010			September 30, 2010
Derivatives in Fair Value Hedging Relationships	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income

Commodity derivatives	Operating revenue	$	10,421		$	18,430
Fair value adjustment for natural gas inventory designated as the hedged item	Operating revenue	(10,247		)	(18,425		)
		$	174		$	5

Cash Flow Hedging

Derivative Instruments, Gain (Loss)

Cash flow hedges included in Accumulated Other Comprehensive Income



Three Months Ended September 30, 2011
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	(6,958	)	Interest expense	$	(1,930	)		$	—
Commodity derivatives	10,095			Operating revenue	1,516			Operating revenue	—
Total	$	3,137			$	(414	)		$	—



Three Months Ended September 30, 2010
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	30,227		Interest expense	$	(1,859	)		$	—
Commodity derivatives	(24,912		)	Operating revenue	14,540			Operating revenue	(134		)
Total	$	5,315			$	12,681			$	(134	)



Nine Months Ended September 30, 2011
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	(11,428	)	Interest expense	$	(5,741	)		$	—
Commodity derivatives	9,784			Operating revenue	2,849			Operating revenue	—
Total	$	(1,644	)		$	(2,892	)		$	—



Nine Months Ended September 30, 2010
Derivatives in Cash Flow Hedging Relationships	Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)			Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)	Amount of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion)			Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)
Interest rate swaps	$	18,341		Interest expense	$	(5,683	)		$	—
Commodity derivatives	(18,822		)	Operating revenue	12,592			Operating revenue	(451		)
Total	$	(481	)		$	6,909			$	(451	)

Derivatives Not Designated as Hedge Instruments

Derivative Instruments, Gain (Loss)

Gains and losses recognized in income



		Three Months Ended			Nine Months Ended
		September 30, 2011			September 30, 2011
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income
Commodity derivatives	Operating revenue	$	(18,529	)	$	(14,321	)
Interest rate swaps - unrealized	Interest rate swaps — unrealized (loss) gain	(38,246		)	(40,608		)
Interest rate swaps - realized	Interest expense	(3,373		)	(10,077		)
Foreign currency contracts	Operating revenue	—			(143		)
		$	(60,148	)	$	(65,149	)



		Three Months Ended			Nine Months Ended
		September 30, 2010			September 30, 2010
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income			Amount of Gain/(Loss) on Derivatives Recognized in Income
Commodity derivatives	Operating revenue	$	9,589		$	13,798
Interest rate swaps - unrealized	Interest rate swaps — unrealized (loss) gain	(13,710		)	(41,663		)
Interest rate swaps - realized	Interest expense	(3,773		)	(9,953		)
Foreign currency contracts	Operating revenue	3			(12		)
		$	(7,891	)	$	(37,830	)

- Definition

Tabular disclosure of the location and amount of gains and losses reported in the statement of financial performance, or when applicable, the statement of financial position. For example, (a) gains and losses recognized in the income statement on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges and (b) gains and losses initially recognized in other comprehensive income on derivative instruments designated and qualifying as cash flow hedges.

+ References + Details

Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2011

Fair Value of Financial Instruments [Abstract]

Fair value of financial instruments

The estimated fair value of our financial instruments was as follows (in thousands):



	September 30, 2011				December 31, 2010				September 30, 2010
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents	$	74,779	$	74,779	$	32,438	$	32,438	$	58,975	$	58,975
Restricted cash	$	4,080	$	4,080	$	4,260	$	4,260	$	17,082	$	17,082
Derivative financial instruments - assets	$	65,942	$	65,942	$	65,832	$	65,832	$	84,450	$	84,450
Derivative financial instruments - liabilities	$	155,766	$	155,766	$	100,528	$	100,528	$	134,210	$	134,210
Notes payable	$	359,000	$	359,000	$	249,000	$	249,000	$	145,000	$	145,000
Long-term debt, including current maturities	$	1,285,087	$	1,430,271	$	1,191,231	$	1,290,519	$	1,193,607	$	1,303,338

- Definition

Tabular disclosure of the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments, assets, and liabilities. Such certain disclosures about the financial instruments, assets, and liabilities include: (1) the fair value of the required items together with their carrying amounts (as appropriate) and (2) the methodology and assumptions used in developing such estimates of fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 14
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15
-Subparagraph b-d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph a, c(1), c(2), c(3), d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph c(2), d, e, f
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 19
-Subparagraph a, b, c(1), d(1)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13467-108611

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13476-108611

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6447952&loc=d3e13220-108610

+ Details

Management's Statement (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Management's Statement (Details) - USD ($) $ in Millions	Sep. 30, 2010	Sep. 30, 2010
Improperly eliminated transactions with the rate regulated operations [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Overstatement of Utility and Non-regulated revenue and Fuel, purchased power and cost of gas sold in aggregate	$ 14.8	$ 45.6

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Non-cash investing activities
Property, plant and equipment acquired with accrued liabilities	$ 49,566	$ 37,661
Cash (paid) refunded during the period for
Interest (net of amounts capitalized)	(61,461)	(62,740)
Income taxes, net	$ 11,826	$ (488)

Materials, Supplies and Fuel (Details) - USD ($)
$ in Thousands

Sep. 30, 2011

Dec. 31, 2010

Sep. 30, 2010

Materials, supplies and fuel

$ 134,463

$ 139,677

$ 145,251

Materials and supplies

37,611

31,749

31,192

Electric Utilities

Fuel - Electric Utilities

8,639

9,687

9,056

Gas Utilities [Member]

Natural gas in storage - Gas Utilities

38,641

21,691

36,782

Energy Marketing [Member]

Commodities held by Energy Marketing

49,572

^[1]

76,550

^[1]

68,221

Market adjustments

$ (1,700)

$ (9,100)

$ (18,700)

[1]

As of September 30, 2011, December 31, 2010 and September 30, 2010, market adjustments related to natural gas held by Energy Marketing and recorded in inventory as part of fair value hedge transactions were $(1.7) million, $(9.1) million and $(18.7) million, respectively (see Note 12 for further discussion of Energy Marketing activities).

Accounts Receivable (Details) - USD ($)
$ in Thousands

Sep. 30, 2011

Dec. 31, 2010

Sep. 30, 2010

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

$ 243,545

$ 331,174

$ 236,773

Allowance for Doubtful Accounts Receivable, Current

(1,714)

(2,363)

(2,293)

Accounts Receivable, Net, Current

241,831

328,811

234,480

Electric Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

58,290

70,577

59,914

Allowance for Doubtful Accounts Receivable, Current

(590)

(708)

(927)

Accounts Receivable, Net, Current

57,700

69,869

58,987

Gas Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

33,686

82,346

30,718

Allowance for Doubtful Accounts Receivable, Current

(789)

(1,425)

(830)

Accounts Receivable, Net, Current

32,897

80,921

29,888

Oil and Gas

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

8,820

6,213

6,112

Allowance for Doubtful Accounts Receivable, Current

(161)

Accounts Receivable, Net, Current

8,659

6,052

5,951

Coal Mining

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

1,845

2,420

2,201

Allowance for Doubtful Accounts Receivable, Current

Accounts Receivable, Net, Current

1,845

2,420

2,201

Energy Marketing [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

139,332

157,064

99,850

Allowance for Doubtful Accounts Receivable, Current

(174)

(69)

(375)

Accounts Receivable, Net, Current

139,158

156,995

99,475

Power Generation

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

119

307

463

Allowance for Doubtful Accounts Receivable, Current

Accounts Receivable, Net, Current

119

307

463

Corporate

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

1,453

12,247

37,515

Allowance for Doubtful Accounts Receivable, Current

Accounts Receivable, Net, Current

1,453

12,247

^[1]

37,515

^[1],[2]

Billed Revenues [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

214,626

271,226

207,707

Billed Revenues [Member] | Electric Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

41,889

51,005

41,955

Billed Revenues [Member] | Gas Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

21,168

41,970

19,611

Billed Revenues [Member] | Oil and Gas

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

8,820

6,213

6,112

Billed Revenues [Member] | Coal Mining

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

1,845

2,420

2,201

Billed Revenues [Member] | Energy Marketing [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

139,332

157,064

99,850

Billed Revenues [Member] | Power Generation

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

119

307

463

Billed Revenues [Member] | Corporate

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

1,453

12,247

37,515

Unbilled Revenues [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

28,919

59,948

29,066

Unbilled Revenues [Member] | Electric Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

16,401

19,572

17,959

Unbilled Revenues [Member] | Gas Utilities

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

12,518

40,376

11,107

Unbilled Revenues [Member] | Oil and Gas

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

Unbilled Revenues [Member] | Coal Mining

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

Unbilled Revenues [Member] | Energy Marketing [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

Unbilled Revenues [Member] | Power Generation

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

Unbilled Revenues [Member] | Corporate

Accounts, Notes, Loans and Financing Receivable [Line Items]

Accounts Receivable, Gross, Current

$ 0

[1]	(a) During the third quarter of 2010 we reached a settlement with the IRS and received a refund relating to this settlement during 2011 of $12.0 million, excluding interest income.
[2]	(b) includes cash collateral receivable on de-designated interest rate swaps. See Note 12 for further information.

Accounts Receivable Income Tax Receivable (Details) $ in Millions	9 Months Ended
	Sep. 30, 2011 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from Income Tax Refunds	$ 12.0

Notes Payable Line of Credit Facility (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Line of Credit Facility
Notes Payable	$ 359,000	$ 145,000	$ 359,000	$ 145,000	$ 249,000
Letters of Credit, Amount Outstanding	174,980	147,000	174,980	147,000	213,800
Consolidated Net Worth: Actual	1,088,005	1,080,407	1,088,005	1,080,407	1,100,270
Enserco Credit Facility [Member]
Line of Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity	250,000		$ 250,000
Line of Credit Facility, Expiration Date			5/7/2012
Line of Credit Accordion Feature	$ 350,000		$ 350,000
Line of Credit Facility, Sub-Limit on Maximum Borrowing Capacity			$ 50,000
Enserco Credit Facility [Member] \| Base Rate Option
Line of Credit Facility
Line of Credit Facility, Interest Rate at Period End	1.75%		1.75%
Enserco Credit Facility [Member] \| Eurodollar Option
Line of Credit Facility
Line of Credit Facility, Interest Rate at Period End	2.50%		2.50%
Line of Credit [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility
Notes Payable	$ 209,000	145,000	$ 209,000	145,000	149,000
Letters of Credit, Amount Outstanding	42,355	15,500	42,355	15,500	46,900
Line of Credit Facility, Current Borrowing Capacity	500,000		500,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 600,000		$ 600,000
Line of Credit Facility, Expiration Date			4/14/2013
Line of Credit Facility, Commitment Fee Percentage			0.50%
Line of Credit Facility, Interest Rate at Period End	2.75%		2.75%
Deferred Financing Costs Remaining on Balance Sheet	$ 1,970		$ 1,970
Amortization Expense	473	481	1,419	866
Consolidated Net Worth: Actual	1,088,000		1,088,000
Line of Credit, Covenant Requirement, Consolidated Net Worth, Minimum	$ 871,300		$ 871,300
Recourse Leverage Ratio	61.30%		61.30%
Line of Credit, Covenant Requirement, Recourse Leverage Ratio	65.00%		65.00%
Line of Credit [Member] \| Revolving Credit Facility [Member] \| Base Rate Option
Line of Credit Facility
Line of Credit Facility, Interest Rate at Period End	1.75%		1.75%
Line of Credit [Member] \| Revolving Credit Facility [Member] \| Eurodollar Option
Line of Credit Facility
Line of Credit Facility, Interest Rate at Period End	2.75%		2.75%
Line of Credit [Member] \| Enserco Credit Facility [Member]
Line of Credit Facility
Notes Payable	$ 0	0	$ 0	0	0
Letters of Credit, Amount Outstanding	132,625	131,500	132,625	131,500	166,900
Deferred Financing Costs Remaining on Balance Sheet	812		812
Amortization Expense	305	263	866	1,245
Corporate Term Loan due June 2012 [Member] \| Loans Payable [Member]
Line of Credit Facility
Notes Payable	150,000	0	150,000	0	0
Letters of Credit, Amount Outstanding	0	0	0	0	0
Corporate Term Loan due in 2011 [Member] \| Loans Payable [Member]
Line of Credit Facility
Notes Payable	0	0	0	0	100,000
Letters of Credit, Amount Outstanding	$ 0	$ 0	$ 0	$ 0	$ 0

Notes Payable Corporate Term Loan (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Short-term Debt [Line Items]
Long-term debt, net of current maturities	$ 1,282,194	$ 1,186,050	$ 1,188,293
Notes Payable	359,000	249,000	145,000
Notes Payable to Banks [Member]
Short-term Debt [Line Items]
Long-term debt, net of current maturities	$ 100,000
Term Loan, Due Date	Sep. 30, 2013
Loans Payable [Member] \| Corporate Term Loan due June 2012 [Member]
Short-term Debt [Line Items]
Notes Payable	$ 150,000	$ 0	$ 0
Term Loan, Due Date	Jun. 24, 2012
Interest Rate at Period End	1.63%
Loans Payable [Member] \| Corporate Term Loan due June 2012 [Member] \| LIBOR [Member]
Short-term Debt [Line Items]
Debt Instrument, Spread on Variable Rate, Basis Points	125

Earnings per Share Reconcilation of Basic to Dilutive Shares (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)	$ (10,525)	$ 12,390	$ 24,137	$ 35,165
Weighted average shares - basic	39,145	38,933	39,105	38,895
Dilutive effect of:
Restricted stock	0	131	147	110
Stock Options	0	12	16	9
Forward equity issuance	0	0	473	0
Other Stock	0	57	51	38
Weighted average shares - diluted	39,145	39,133	39,792	39,052

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 87-21
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 10, 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28, 29, 30
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 03
-Paragraph 19

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 20
-Article 9

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=6519514

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.18)
-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.19)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e565-108580

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.22)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph A7
-Appendix A

+ Details

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References + Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 171
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 40
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=6920599&loc=d3e1448-109256

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Weighted-Average Number of Common Shares Outstanding
-URI http://asc.fasb.org/extlink&oid=6528421

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 07-4
-Paragraph 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Earnings per Share Anti-dilutive shares (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	223	131	155	172
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	176	128	119	169
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	20	2	17	2
Other Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	27	1	19	1

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 13, 14
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 171
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 40
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Diluted Earnings Per Share
-URI http://asc.fasb.org/extlink&oid=6510752

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Stock Agreement
-URI http://asc.fasb.org/extlink&oid=6508534

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 07-4
-Paragraph 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Earnings per Share Potentially dilutive shares: (Details)	3 Months Ended
	Sep. 30, 2011 shares
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Securities Excluded From Diluted Earnings Per Share Due To Net Loss	11,880
Restricted Stock and Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Securities Excluded From Diluted Earnings Per Share Due To Net Loss	159,873
Forward Equity Agreement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Securities Excluded From Diluted Earnings Per Share Due To Net Loss	424,715
Other Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Securities Excluded From Diluted Earnings Per Share Due To Net Loss	31,408

Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net income (loss)	$ (10,525)	$ 12,390	$ 24,137	$ 35,165
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments	0	0	0	(8)
Taxes on benefit plan liability adjustment	0	0	0	(7)
Benefit plan liability adjustments, net of tax	0	0	0	(15)
Fair value adjustment on derivatives designated as cash flow hedges	3,137	517	(1,644)	495
Taxes on fair value adjustment on derivatives designated as cash flow hedges	(1,215)	486	653	641
Fair value adjustment on derivatives designated as cash flow hedges, net of tax	1,922	1,003	(991)	1,136
Reclassification adjustments on cash flow hedges settled and included in net income (loss)	414	(4,730)	2,892	(6,909)
Taxes on reclassification adjustment on cash flow hedges settled and included in net income (loss)	(129)	1,761	(985)	2,543
Reclassification adjustments on cash flow hedges settled and included in net income (loss), net of tax	285	(2,969)	1,907	(4,366)
Comprehensive income (loss)	$ (8,318)	$ 10,424	$ 25,053	$ 31,920

Comprehensive Income (Loss) Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Derivatives designated as cash flow hedges	$ (11,523)	$ (12,437)	$ (12,741)
Employee benefit plans	(11,142)	(11,142)	(9,636)
Amount from equity-method investees	0	(2)	(32)
Total	$ (22,665)	$ (23,581)	$ (22,409)

- Definition

The total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 26
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph i
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 158
-Paragraph 7
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e637-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e681-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e653-108580

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

+ Details

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References

+ Details

Common Stock (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
Common Stock (Details) $ / shares in Units, $ in Millions	Sep. 30, 2011 USD ($) $ / shares	Sep. 30, 2010 USD ($)	Sep. 30, 2011 USD ($) years $ / shares shares	Sep. 30, 2010 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 8.5		$ 8.5
Allocated Share-based Compensation Expense	$ 1.7	$ 1.9	$ 5.0	$ 4.7
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition \| years			2
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares			67,389
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			Jan. NaN, 2011
Performance Share Award, Percentage of Target, Minimum	0.00%		0.00%
Performance Share Award, Percentage of Target, Maximum	175.00%		175.00%
Performance Share Award Payout, Cash Percentage	50.00%		50.00%
Performance Share Award Payout, Shares of Common Stock Percentage	50.00%		50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares			$ 25.91
Short-term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period \| shares			14,111
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost			$ 0.4
Restricted
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares			136,348
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 4.1		$ 4.1
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			3 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures \| shares			99,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price \| $ / shares	$ 32.04		$ 32.04
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Total Fair Value			$ 0.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period \| shares			5,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price \| $ / shares	$ 29.94		$ 29.94
Proceeds from Stock Options Exercised			$ 0.2

Common Stock Dividend Reinvestment and Stock Purchase Plan (Details) - DRIP [Member]	9 Months Ended
	Sep. 30, 2011 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock purchase, Percentage of Recent Average Market Price	100.00%
Stock Issued During Period, Shares, Dividend Reinvestment Plan	79,339
Weighted Average Price of Shares, Dividend Reinvestment Plan \| $ / shares	$ 30.81
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	476,437

Common Stock Dividend Restrictions (Details) - Revolving Credit Facility - Cash Dividends [Member] $ in Millions	Sep. 30, 2011 USD ($)
Line of Credit Facility
Line of Credit, Covenant, Recourse Leverage Ratio, Minimum	0.65
Line of Credit, Covenant, Recourse Leverage Ratio, Maximum	1
Line of Credit, Covenant, Consolidated Net Worth, Minimum Requirement	$ 625
Line of Credit, Covenant, Percentage of Aggregate Consolidated Net Income	50.00%

Common Stock Dividend Restrictions Subsidiaries (Details) $ in Millions	Sep. 30, 2011 USD ($)
Utilities Group [Member]
Amount of Restricted Net Assets for Subsidiaries	$ 164.3
Enserco Credit Facility
Amount of Restricted Net Assets for Subsidiaries	163.8
Non Regulated Energy Group [Member]
Amount of Restricted Net Assets for Subsidiaries	$ 100.0

Common Stock Forward Equity Issuance (Details) $ in Millions	9 Months Ended
	Sep. 30, 2011 USD ($) shares
Forward Equity Agreement [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares	4,000,000
Forward Equity Issuance OverAllotment	413,519
Forward Equity Issuance Total Shares	4,413,519
Forward Equity Agreement [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Equity Shares Issued, Value, New Issues \| $	$ 119.6

Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,355	$ 1,533	$ 4,066	$ 4,599
Interest cost	3,732	3,773	11,196	11,319
Expected return on plan assets	(4,239)	(3,623)	(12,717)	(10,869)
Prior service cost	25	305	75	915
Net loss (gain)	1,135	500	3,405	1,500
Curtailment expense	0	0	0	0
Net periodic benefit cost	2,008	2,488	6,025	7,464
Contributions Made	10,500		11,050
Contributions Remaining in Current Fiscal Year	0		0
Contributions Anticipated in Next Fiscal Year	7,869		7,869
Non-pension Postretirement Healthcare Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	375	377	1,125	1,131
Interest cost	542	611	1,626	1,833
Expected return on plan assets	(41)	(52)	(123)	(156)
Prior service cost	(120)	(77)	(360)	(231)
Net transition obligation	0	0	0	0
Net loss (gain)	169	159	507	477
Net periodic benefit cost	925	1,018	2,775	3,054
Contributions Made	882		2,646
Contributions Remaining in Current Fiscal Year	882		882
Contributions Anticipated in Next Fiscal Year	3,765		3,765
Supplemental Non-qualified Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	257	171	771	513
Interest cost	324	321	973	963
Prior service cost	1	1	3	3
Net loss (gain)	128	71	383	213
Net periodic benefit cost	710	$ 564	2,130	$ 1,692
Contributions Made	235		705
Contributions Remaining in Current Fiscal Year	236		236
Contributions Anticipated in Next Fiscal Year	$ 896		$ 896

Summary of Information Relating to Segments of our Business Income Statement (Details) - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2011

Sep. 30, 2010

Sep. 30, 2011

Sep. 30, 2010

Segment Reporting Information

Inter-segment Operating Revenue

$ 0

$ 1,128

$ 0

$ 3,383

Total external operating revenues

256,460

248,366

932,885

928,949

Net income (loss)

(10,525)

12,390

24,137

35,165

Electric Utilities

Segment Reporting Information

External Operating Revenue

151,063

138,761

431,624

415,092

Inter-segment Operating Revenue

^[1]

2,653

2,884

9,902

11,627

Net income (loss)

15,790

18,537

^[2]

34,653

35,585

^[2]

Significant Acquisitions and Disposals, Gain (Loss) on Sale or Disposal, Net of Tax Included in Net Income

4,100

Gas Utilities

Segment Reporting Information

External Operating Revenue

72,651

72,323

402,839

402,608

Inter-segment Operating Revenue

Net income (loss)

572

(595)

^[3]

24,275

18,017

^[3]

Significant Acquisitions and Disposals, Gain (Loss) on Sale or Disposal, Net of Tax Included in Net Income

1,700

Oil and Gas

Segment Reporting Information

External Operating Revenue

19,163

19,354

55,907

57,755

Inter-segment Operating Revenue

Net income (loss)

241

836

^[4]

(553)

3,405

^[4]

Tax Adjustments, Settlements, and Unusual Provisions

400

Power Generation

Segment Reporting Information

External Operating Revenue

1,011

1,124

2,750

3,266

Inter-segment Operating Revenue

7,089

6,731

^[1]

20,750

19,336

^[1]

Net income (loss)

337

575

2,071

1,239

Coal Mining

Segment Reporting Information

External Operating Revenue

9,184

7,744

23,064

22,431

Inter-segment Operating Revenue

8,651

6,533

^[1]

25,806

20,875

^[1]

Net income (loss)

555

1,673

(1,124)

6,093

Energy Marketing [Member]

Segment Reporting Information

External Operating Revenue

3,388

9,060

16,701

27,797

Inter-segment Operating Revenue

3,550

(87)

5,178

(157)

Net income (loss)

273

1,370

1,327

4,890

Corporate Elimination [Member]

Segment Reporting Information

External Operating Revenue

Inter-segment Operating Revenue

Net income (loss)

^[5]

(27,943)

(10,093)

^[6]

(36,101)

(34,221)

^[6]

Increase Decrease in Fair Value of Derivative Instruments Not Designated as Hedging Instruments Net of Tax Included in Net Income

(24,900)

(8,900)

(26,400)

(27,100)

Tax Adjustments, Settlements, and Unusual Provisions

2,000

Intersegment Elimination [Member]

Segment Reporting Information

External Operating Revenue

Inter-segment Operating Revenue

(21,943)

(14,933)

^[1]

(61,636)

(48,298)

Net income (loss)

$ (350)

$ 87

$ (411)

$ 157

[1]	Total operating revenue has been restated to reflect elimination of intercompany activities previously not eliminated. See Note 1 for further information.
[2]	Net income (loss) includes a $4.1 million after-tax gain on sale of a 23% interest in Wygen III to the City of Gillette.
[3]	Net income (loss) includes a $1.7 million after-tax gain on sale of operating assets in the Gas Utilities at Nebraska Gas.
[4]	Net income (loss) includes a $0.4 million reduction of income taxes as a result of a re-measurement of a previously reported uncertain tax position due to a settlement with the IRS.
[5]	Net income (loss) includes a $24.9 million and a $26.4 million net after-tax mark-to-market loss on interest rate swaps for the three and nine months ended September 30, 2011 and an $8.9 million and $27.1 million net after-tax loss on interest rate swaps for the three and nine months ended September 30, 2010, respectively.
[6]	Net income (loss) includes a $2.0 million reduction in income tax expense reflecting a re-measurement of an uncertain tax position due to a settlement agreement that was reached with the IRS primarily due to tax depreciation method changes.

Summary of Information Relating to Segments of our Business Assets (Details) - USD ($)
$ in Thousands

Sep. 30, 2011

Dec. 31, 2010

Sep. 30, 2010

Segment Reporting, Asset Reconciling Item

Total Assets

$ 3,953,367

$ 3,711,509

$ 3,540,237

Electric Utilities

Segment Reporting, Asset Reconciling Item

Total Assets

1,917,183

^[1]

1,834,019

^[1]

1,771,014

Gas Utilities

Segment Reporting, Asset Reconciling Item

Total Assets

683,163

722,287

659,801

Oil and Gas

Segment Reporting, Asset Reconciling Item

Total Assets

405,513

349,991

358,113

Power Generation

Segment Reporting, Asset Reconciling Item

Total Assets

372,313

^[1]

293,334

^[1]

249,778

Coal Mining

Segment Reporting, Asset Reconciling Item

Total Assets

94,908

96,962

94,149

Energy Marketing [Member]

Segment Reporting, Asset Reconciling Item

Total Assets

340,499

314,930

287,173

Unallocated Amount to Segment [Member]

Segment Reporting, Asset Reconciling Item

Total Assets

$ 139,788

$ 99,986

$ 120,209

[1]	Includes construction of a 180 MW power generation facility by our Colorado Electric utility and a 200 MW power generation facility by our Power Generation segment; both facilities are currently under construction and are expected to be completed by December 31, 2011.

Risk Management Activities (Details)
mW in Thousands, T in Thousands, $ in Thousands

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2011

USD ($)

bbl

Btu

Dec. 31, 2010

USD ($)

bbl

Btu

Sep. 30, 2010

USD ($)

bbl

Btu

Sep. 30, 2011

USD ($)

bbl

Btu

Sep. 30, 2010

USD ($)

bbl

Btu

Dec. 31, 2010

USD ($)

bbl

Btu

Trading Activities [Abstract]

Current derivative assets

$ 48,727

$ 56,572

$ 71,688

$ 48,727

$ 71,688

$ 56,572

Non-current derivative assets

17,215

9,260

12,762

17,215

12,762

9,260

Current derivative liabilities

129,163

79,167

108,318

129,163

108,318

79,167

Non-current derivative liabilities

26,603

21,361

25,892

26,603

25,892

21,361

Unrealized Gain (Loss) on Derivatives

(9,605)

10,690

Financing Activities | Interest Rate Swaps, Designated

Trading Activities [Abstract]

Current derivative liabilities

6,724

6,823

6,901

6,724

6,901

6,823

Non-current derivative liabilities

21,108

14,976

21,518

21,108

21,518

14,976

Cash collateral (receivable)/payable included in derivative assets/liabilities

$ 0

Maximum Length of Time Hedged in Cash Flow Hedge (years)

5.25

6.25

Interest Rate Derivatives [Abstract]

Notional Amount of Interest Rate Derivatives

$ 150,000

Derivative, Average Interest Rate

5.04%

Accumulated Other Comprehensive Income Loss PreTax

$ (27,832)

$ (21,799)

$ (28,419)

$ (27,832)

$ (28,419)

$ (21,799)

Gain (Loss) on Derivative Instruments, Net, Pretax

$ 0

Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net

$ (6,724)

Financing Activities | Interest Rate Swaps, Dedesignated

Trading Activities [Abstract]

Latest Expiration, Maximum terms (months)

^[1]

.25

Current derivative liabilities

$ 94,588

$ 53,980

$ 80,450

$ 94,588

$ 80,450

$ 53,980

Non-current derivative liabilities

Cash collateral (receivable)/payable included in derivative assets/liabilities

25,000

Interest Rate Derivatives [Abstract]

Notional Amount of Interest Rate Derivatives

$ 250,000

Derivative, Average Interest Rate

5.67%

Accumulated Other Comprehensive Income Loss PreTax

$ 0

Gain (Loss) on Derivative Instruments, Net, Pretax

$ (40,608)

$ (15,193)

$ (41,663)

Financing Activities | Interest Rate Swaps, Dedesignated | Dedesignated Interest Rate Swap Expiring 2018 [Member]

Trading Activities [Abstract]

Derivative, Remaining Maturity (months)

7.25

Interest Rate Derivatives [Abstract]

Notional Amount of Interest Rate Derivatives

$ 100,000

Financing Activities | Interest Rate Swaps, Dedesignated | Dedesignated Interest Rate Swaps Expiring 2028 [Member]

Trading Activities [Abstract]

Derivative, Remaining Maturity (months)

17.25

Interest Rate Derivatives [Abstract]

Notional Amount of Interest Rate Derivatives

$ 150,000

Oil and Gas [Member] | Oil and Gas Exploration and Production

Trading Activities [Abstract]

Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months

$ 8,300

Oil and Gas [Member] | Oil and Gas Exploration and Production | Natural Gas | Swap

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

^[2]

4,957,250

6,821,800

8,109,800

4,957,250

8,109,800

6,821,800

Current derivative assets

$ 6,937

$ 7,675

$ 8,816

$ 6,937

$ 8,816

$ 7,675

Non-current derivative assets

717

2,606

4,523

717

4,523

2,606

Current derivative liabilities

Non-current derivative liabilities

$ 7

$ 0

Maximum Length of Time Hedged in Cash Flow Hedge (years)

^[3]

.25

0.25

.25

Earnings

$ 0

Interest Rate Derivatives [Abstract]

Accumulated Other Comprehensive Income Loss PreTax

$ 7,647

$ 10,281

$ 13,339

$ 7,647

$ 13,339

$ 10,281

Oil and Gas [Member] | Oil and Gas Exploration and Production | Crude Oil | Swaps and Options [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | bbl

^[2]

414,000

424,500

484,500

414,000

484,500

424,500

Current derivative assets

$ 1,885

$ 248

$ 466

$ 1,885

$ 466

$ 248

Non-current derivative assets

2,529

216

2,529

216

Current derivative liabilities

3,814

3,224

3,814

Non-current derivative liabilities

$ 0

$ 1,301

$ 497

497

1,301

Maximum Length of Time Hedged in Cash Flow Hedge (years)

^[3]

0.25

.25

Earnings

$ 157

$ 465

$ 572

Interest Rate Derivatives [Abstract]

Accumulated Other Comprehensive Income Loss PreTax

4,257

(5,313)

(3,611)

4,257

(3,611)

(5,313)

Gas Utilities [Member] | Regulated Gas Utilities - Gas Hedges

Trading Activities [Abstract]

Current derivative assets

3,355

4,787

6,685

3,355

6,685

4,787

Non-current derivative assets

Non-current derivative liabilities

1,360

1,620

2,600

1,360

2,600

1,620

Cash collateral (receivable)/payable included in derivative assets/liabilities

12,058

10,355

20,519

12,058

20,519

10,355

Net Unrealized Gain (Loss) Included in Regulatory Assets

(11,813)

(8,030)

(18,381)

(11,813)

(18,381)

(8,030)

Option Premium Included in Derivative Assets, Current

$ 1,750

$ 842

$ 1,947

$ 1,750

$ 1,947

$ 842

Gas Utilities [Member] | Regulated Gas Utilities - Gas Hedges | Natural Gas | Commodity Option | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

3,880,000

1,730,000

3,980,000

3,880,000

3,980,000

1,730,000

Derivative, Remaining Maturity (months)

Gas Utilities [Member] | Regulated Gas Utilities - Gas Hedges | Natural Gas | Future | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

9,890,000

6,670,000

11,800,000

9,890,000

11,800,000

6,670,000

Derivative, Remaining Maturity (months)

Gas Utilities [Member] | Regulated Gas Utilities - Gas Hedges | Natural Gas | Basis Swap [Member] | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

Derivative, Remaining Maturity (months)

Energy Marketing [Member]

Trading Activities [Abstract]

Derivative, Net Liability Position, Aggregate Fair Value

$ 0

Inventory Market Adjustment

1,700

9,100

18,700

1,700

18,700

9,100

Collateral, included in other current assets

34,642

9,919

1,854

34,642

1,854

9,919

Collateral, included in other current liabilities

(802)

(1,079)

(802)

(1,079)

Foreign Currency Derivatives [Abstract]

Fair Value, Foreign Exchange Contracts

(143)

(11)

(143)

Unrealized foreign exchange gain (loss)

783

621

181

Realized foreign exchange gain (loss)

(529)

(61)

(91)

(652)

Energy Marketing [Member] | Forward Contracts | Purchase Contract [Member]

Foreign Currency Derivatives [Abstract]

Canadian dollars purchased, Outstanding Notional Amounts

$ 0

$ 15,000

$ 5,000

$ 0

$ 5,000

$ 15,000

Latest Expiration (Months)

Energy Marketing [Member] | Forward Contracts | Sell Contract [Member]

Foreign Currency Derivatives [Abstract]

Canadian dollars sold, Outstanding Notional Amounts

$ 0

Latest Expiration (Months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing

Trading Activities [Abstract]

Current derivative assets

$ 36,550

$ 43,862

$ 55,366

$ 36,550

$ 55,366

$ 43,862

Non-current derivative assets

13,969

6,635

8,023

13,969

8,023

6,635

Current derivative liabilities

27,851

14,550

17,743

27,851

17,743

14,550

Non-current derivative liabilities

4,128

3,464

1,277

4,128

1,277

3,464

Cash collateral (receivable)/payable included in derivative assets/liabilities

9,026

3,958

(7,365)

$ 9,026

$ (7,365)

$ 3,958

Unrealized Gain (Loss) on Derivatives

$ 9,514

$ 28,525

$ 51,734

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Basis Swap Commodity | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

425,360,000

399,128,000

335,805,000

425,360,000

335,805,000

399,128,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Basis Swap Commodity | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

443,489,000

426,903,000

358,929,000

443,489,000

358,929,000

426,903,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Commodity Option | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

6,000,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Commodity Option | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

6,000,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Forward Contracts | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

105,446,000

144,948,000

135,818,000

105,446,000

135,818,000

144,948,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Forward Contracts | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

122,232,000

143,021,000

136,530,000

122,232,000

136,530,000

143,021,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Future | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

78,100,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Future | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

96,730,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Fixed-for-float Swaps | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

251,602,000

135,005,000

84,636,000

251,602,000

84,636,000

135,005,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Natural Gas | Fixed-for-float Swaps | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | Btu

249,808,000

150,803,000

97,210,000

249,808,000

97,210,000

150,803,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Crude Oil | Forward Contracts | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | bbl

7,326,000

5,628,000

5,561,000

7,326,000

5,561,000

5,628,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Crude Oil | Forward Contracts | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | bbl

7,917,000

6,921,000

4,759,000

7,917,000

4,759,000

6,921,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Crude Oil | Fixed-for-float Swaps | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | bbl

20,000

135,000

20,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Crude Oil | Fixed-for-float Swaps | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | bbl

10,000

240,000

289,000

10,000

289,000

240,000

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Commodity Option | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

4,530

2,835

1,980

4,530

1,980

2,835

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Commodity Option | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

572

270

360

572

360

270

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Forward Contracts | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

27,982

24,634

24,100

27,982

24,100

24,634

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Forward Contracts | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

13,331

9,046

6,213

13,331

6,213

9,046

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Fixed-for-float Swaps | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

8,305

4,060

5,585

8,305

5,585

4,060

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Coal | Fixed-for-float Swaps | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | T

9,710

3,720

4,445

9,710

4,445

3,720

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Power | Forward Contracts | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

153

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Power | Forward Contracts | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

153

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Power | Fixed-for-float Swaps | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

12,370

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Power | Fixed-for-float Swaps | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

12,439

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Environmental Prodcuts [Member] | Forward Contracts | Purchase Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

283

Derivative, Remaining Maturity (months)

Energy Marketing [Member] | Natural Gas, Crude Oil, Coal, Power and Environmental Marketing | Environmental Prodcuts [Member] | Forward Contracts | Sell Contract [Member]

Trading Activities [Abstract]

Derivative, Nonmonetary Notional Amount | mW

273

Derivative, Remaining Maturity (months)

[1]	Maximum terms in years reflect the amended mandatory early termination dates. If the mandatory early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended annually, de-designated swaps totaling $100 million terminate in 7.25 years and de-designated swaps totaling $150 million terminate in 17.25 years.
[2]	Crude oil in Bbls, gas in MMBtus
[3]	Refers to the term of the derivative instrument. Assets and liabilities are classified as current or non-current based on the timing of the hedged transaction and the corresponding settlement of the derivative instruments.

Fair Value Measurements Fair Value Heirarchy Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Cash Collateral [Member]
Recurring Fair Value Measures
Derivative, Collateral Payable (Receivable) Net, Netted in Derivatives	$ 21,100	$ 14,300	$ 13,200
Fair Value, Measurements, Recurring [Member] \| Level 1
Recurring Fair Value Measures
Money Market Funds	9,006	8,050	10,050
Assets, Total	9,006	8,050	10,050
Liabilities, Total	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2
Recurring Fair Value Measures
Money Market Funds	0	0	0
Assets, Total	373,623	171,284	221,817
Liabilities, Total	489,433	226,072	287,697
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	370,586	166,405	221,740
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	365,646	143,537	172,401
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	11,740	10,281	13,459
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	7	5,115	3,720
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	(8,703)	(5,568)	(13,382)
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	1,360	1,620	2,696
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		166	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	21	11
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	122,420	75,779	108,869
Fair Value, Measurements, Recurring [Member] \| Level 3
Recurring Fair Value Measures
Money Market Funds	0	0	0
Assets, Total	9,521	8,242	3,808
Liabilities, Total	4,619	2,463	840
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	9,193	7,976	3,246
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	4,619	2,463	840
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	328	266	562
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral
Recurring Fair Value Measures
Money Market Funds	0	0	0
Assets, Total	(325,992)	(122,639)	(154,306)
Liabilities, Total	(325,992)	(122,639)	(154,305)
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	(325,992)	(122,639)	(154,306)
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(325,992)	(122,639)	(154,305)
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Counterparty Netting and Cash Collateral \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member]
Recurring Fair Value Measures
Money Market Funds	0	0	0
Assets, Total	8,790	8,945	13,131
Liabilities, Total	(12,294)	(5,368)	(22)
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member] \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	(3,268)	(1,410)	(7,387)
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(12,294)	(5,368)	(22)
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member] \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	0	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member] \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	12,058	10,355	20,518
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member] \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Cash Collateral [Member] \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Recurring Fair Value Measures
Money Market Funds	9,006	8,050	10,050
Assets, Total	74,948	73,882	94,500
Liabilities, Total	155,766	100,528	134,210
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Commodity Derivatives \| Energy Marketing [Member]
Recurring Fair Value Measures
Derivative Assets	50,519	50,332	63,293
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	31,979	17,993	18,914
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Commodity Derivatives \| Oil and Gas
Recurring Fair Value Measures
Derivative Assets	12,068	10,547	14,021
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	7	5,115	3,720
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Commodity Derivatives \| Regulated Utilities Group
Recurring Fair Value Measures
Derivative Assets	3,355	4,787	7,136
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	1,360	1,620	2,696
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Foreign Currency Derivatives
Recurring Fair Value Measures
Foreign Currency Contract, Asset, Fair Value Disclosure		166	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	21	11
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Interest Rate Swaps
Recurring Fair Value Measures
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 122,420	$ 75,779	$ 108,869

Fair Value Measurements Changes in Level 3 Recurring Fair Value (Details) - Commodity Derivatives - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2011

Sep. 30, 2010

Sep. 30, 2011

Sep. 30, 2010

Fair Value Assets and Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation RollForward [Roll Forward]

Balance as of beginning of period

$ 6,427

$ 2,176

$ 5,779

$ (556)

Unrealized losses

(4,359)

961

(6,981)

(1,206)

Unrealized gains

2,317

850

7,870

4,576

Purchases

Issuances

Settlements

197

(1,761)

Purchases, issuance and settlements

365

1,170

Transfers into level 3 (a)

^[1]

254

(62)

(78)

Transfers out of level 3(b)

^[2]

(592)

(5)

1,402

Balance at end of period

4,902

2,968

4,902

2,968

Changes in unrealized gains relating to instruments still held as of quarter-end

1,067

$ (528)

1,307

$ 1,283

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset and Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)

(300)

(400)

Trading Gross Margins [Member]

Fair Value Assets and Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation RollForward [Roll Forward]

Gain (Loss) Included in Earnings

$ (1,700)

$ 1,300

[1]	Transfers into level 3 represent assets and liabilities that were previously categorized as a higher level for which the inputs became unobservable.
[2]	Transfers out of level 3 represent assets and liabilities that were previously classified as level 3 for which the lowest significant input became observable during the period.

Fair Value Measurements Fair Value Measures (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Derivatives Designated as Hedges
Derivatives, Fair Value
Derivative Asset, Fair Value, Net	$ 2,672	$ 11,000	$ 20,398
Derivative Liability, Fair Value, Net	28,572	23,367	29,971
Derivatives Not Designated as Hedges
Derivatives, Fair Value
Derivative Asset, Fair Value, Net	464,235	184,050	234,156
Derivative Liability, Fair Value, Net	549,243	220,692	287,496
Commodity Derivatives \| Derivatives Designated as Hedges \| Derivative Assets, Current
Derivatives, Fair Value
Derivative Asset, Fair Value	198	10,952	20,387
Derivative Asset, Fair Value, Gross Liability	2	1,452	1,329
Commodity Derivatives \| Derivatives Designated as Hedges \| Derivative Assets, Noncurrent
Derivatives, Fair Value
Derivative Asset, Fair Value	0	48	11
Derivative Asset, Fair Value, Gross Liability	0	71	0
Commodity Derivatives \| Derivatives Designated as Hedges \| Derivative Liabilities, Current
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	2,474	0	0
Derivative Liability, Fair Value	738	45	219
Commodity Derivatives \| Derivatives Designated as Hedges \| Derivative Liabilities, Noncurrent
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value	0	0	3
Commodity Derivatives \| Derivatives Not Designated as Hedges \| Derivative Assets, Current
Derivatives, Fair Value
Derivative Asset, Fair Value	54,747	149,936	193,431
Derivative Asset, Fair Value, Gross Liability	17,996	113,364	154,470
Commodity Derivatives \| Derivatives Not Designated as Hedges \| Derivative Assets, Noncurrent
Derivatives, Fair Value
Derivative Asset, Fair Value	19,890	12,382	22,321
Derivative Asset, Fair Value, Gross Liability	2,675	3,099	9,032
Commodity Derivatives \| Derivatives Not Designated as Hedges \| Derivative Liabilities, Current
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	344,799	20,588	15,944
Derivative Liability, Fair Value	384,729	42,865	36,703
Commodity Derivatives \| Derivatives Not Designated as Hedges \| Derivative Liabilities, Noncurrent
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	44,799	978	2,460
Derivative Liability, Fair Value	49,255	7,363	6,830
Foreign Currency Derivatives \| Derivatives Not Designated as Hedges \| Derivative Assets, Current
Derivatives, Fair Value
Derivative Asset, Fair Value		166	0
Derivative Asset, Fair Value, Gross Liability		21	11
Foreign Currency Derivatives \| Derivatives Not Designated as Hedges \| Derivative Liabilities, Current
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value	0		0
Interest Rate Swaps \| Derivatives Designated as Hedges \| Derivative Liabilities, Current
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value	6,724	6,823	6,901
Interest Rate Swaps \| Derivatives Designated as Hedges \| Derivative Liabilities, Noncurrent
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value	21,108	14,976	21,519
Interest Rate Swaps \| Derivatives Not Designated as Hedges \| Derivative Liabilities, Current
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value	$ 94,588	$ 53,980	80,450
Interest Rate Swaps \| Derivatives Not Designated as Hedges \| Derivative Liabilities, Noncurrent
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Asset			0
Derivative Liability, Fair Value			$ 0

Fair Value Measurements Hedging Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Fair Value Hedging
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	$ 135	$ 174	$ (123)	$ 5
Fair Value Hedging \| Commodity Derivatives \| Operating Revenue
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	1,235	10,421	(7,502)	18,430
Fair Value Hedging \| Fair value adjustment for natural gas inventory designated as the hedged item \| Operating Revenue
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	(1,100)	(10,247)	7,379	(18,425)
Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	3,137	5,315	(1,644)	(481)
Amount of Reclassfied Gain/(Loss) from AOCI into Income (Effective Portion)	(414)	12,681	(2,892)	6,909
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	(134)	0	(451)
Cash Flow Hedging \| Commodity Derivatives
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	10,095	(24,912)	9,784	(18,822)
Cash Flow Hedging \| Commodity Derivatives \| Operating Revenue
Derivative Instruments, Gain (Loss)
Amount of Reclassfied Gain/(Loss) from AOCI into Income (Effective Portion)	1,516	14,540	2,849	12,592
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	(134)	0	(451)
Cash Flow Hedging \| Interest Rate Swaps
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	(6,958)	30,227	(11,428)	18,341
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	0	0	0
Cash Flow Hedging \| Interest Rate Swaps \| Interest Expense
Derivative Instruments, Gain (Loss)
Amount of Reclassfied Gain/(Loss) from AOCI into Income (Effective Portion)	(1,930)	(1,859)	(5,741)	(5,683)
Derivatives Not Designated as Hedge Instruments
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	(60,148)	(7,891)	(65,149)	(37,830)
Derivatives Not Designated as Hedge Instruments \| Commodity Derivatives \| Operating Revenue
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	(18,529)	9,589	(14,321)	13,798
Derivatives Not Designated as Hedge Instruments \| Interest Rate Swaps \| Interest Rate Swap - Unrealized (Loss) Gain
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	(38,246)	(13,710)	(40,608)	(41,663)
Derivatives Not Designated as Hedge Instruments \| Interest Rate Swaps \| Interest Expense
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	(3,373)	(3,773)	(10,077)	(9,953)
Derivatives Not Designated as Hedge Instruments \| Foreign Currency Derivatives \| Operating Revenue
Derivative Instruments, Gain (Loss)
Amount of Gain/(Loss) on Derivatives Recognized in Income	$ 0	$ 3	$ (143)	$ (12)

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 74,779	$ 32,438	$ 58,975	$ 112,901
Restricted cash	4,080	4,260	17,082
Notes Payable	359,000	249,000	145,000
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	74,779	32,438	58,975
Restricted cash	4,080	4,260	17,082
Derivative financial instruments - assets	65,942	65,832	84,450
Derivative financial instruments - liabilities	155,766	100,528	134,210
Notes Payable	359,000	249,000	145,000
Long-term debt, including current maturities	1,285,087	1,191,231	1,193,607
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	74,779	32,438	58,975
Restricted cash	4,080	4,260	17,082
Derivative financial instruments - assets	65,942	65,832	84,450
Derivative financial instruments - liabilities	155,766	100,528	134,210
Notes payable	359,000	249,000	145,000
Long-term debt, including current maturities	$ 1,430,271	$ 1,290,519	$ 1,303,338

Fair Value of Financial Instruments Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Power Generation [Member]
Restricted Cash - Guaranteed Investment Certificates	$ 1,246	$ 3,626	$ 10,642
Oil and Gas [Member]
Restricted Cash - Guaranteed Investment Certificates			$ 6,200

Commitments and Contingencies (Details) $ in Millions	9 Months Ended
Commitments and Contingencies (Details) $ in Millions	Sep. 30, 2011 USD ($)
Capital Additions 200 MW Generation Facility Colorado IPP [Member] \| Power Generation
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 260.0
Committed Contracts, Equipment Purchases, Percentage Complete	100.00%
Capital Additions 180 MW Generation Facility Colorado Electric Utility [Member] \| Electric Utilities
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 227.0
Committed Contracts, Equipment Purchases, Percentage Complete	100.00%

Guarantees (Details) $ in Millions	9 Months Ended
Guarantees (Details) $ in Millions	Sep. 30, 2011 USD ($)
Agency Agreement Commodity Trading [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 7.0
Capital Additions Office Building Black Hills Utility Holdings [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term	4/1/2011
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 6.0
Natural Gas transportation and Storage Supplier Colorado interstate [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term	7/31/2012
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 10.0
Natural Gas Storage and Transportation Supplier Cross Timbers [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term	6/30/2012
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 7.5
Guarantee Obligation Wind Turbines [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term	1/15/2013
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 33.3

Subsequent Events (Details) - Forward Equity Agreement [Member] shares in Thousands, $ in Millions	9 Months Ended
	Sep. 30, 2011 USD ($) shares
Subsequent Event [Line Items]
Forward Equity Stock Issued, Shares, New Issues \| shares	4,413,519
Forward Equity Shares Issued, Value, New Issues \| $	$ 119.6