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Document and Entity Information Document - USD ($)	3 Months Ended
Document and Entity Information Document - USD ($)	Mar. 31, 2013	Apr. 30, 2013	Jun. 30, 2012
Document Information [Line Items]
Entity Registrant Name	BLACK HILLS CORP /SD/
Entity Central Index Key	0001130464
Document Type	10-Q
Document Period End Date	Mar. 31, 2013
Amendment Flag	false
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		44,442,886
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 1,400,316,896

Condensed Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenue	$ 380,671	$ 365,851
Utilities -
Fuel, purchased power and cost of gas sold	168,173	157,183
Operations and maintenance	65,690	64,760
Non-regulated energy operations and maintenance	21,329	22,595
Depreciation, depletion and amortization	34,781	38,559
Taxes - property, production and severance	10,380	11,510
Other operating expenses	472	1,196
Total operating expenses	300,825	295,803
Operating income	79,846	70,048
Interest charges -
Interest expense incurred (including amortization of debt issuance costs, premiums and discounts and realized settlements on interest rate swaps)	(23,672)	(29,914)
Allowance for funds used during construction - borrowed	74	518
Capitalized interest	266	161
Unrealized gain (loss) on interest rate swaps, net	7,456	12,045
Interest income	285	437
Allowance for funds used during construction - equity	200	277
Other income (expense), net	405	1,472
Total other income (expense)	(14,986)	(15,004)
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes	64,860	55,044
Equity in earnings (loss) of unconsolidated subsidiaries	(86)	(56)
Income tax benefit (expense)	(21,577)	(19,717)
Income (loss) from continuing operations	43,197	35,271
Income (loss) from discontinued operations, net of tax	0	(5,484)
Net income (loss) available for common stock	$ 43,197	$ 29,787
Earnings (loss) per share, Basic -
Income (loss) from continuing operations, per share	$ 0.98	$ 0.81
Income (loss) from discontinued operations, per share	0.00	(0.13)
Total income (loss) per share, Basic	0.98	0.68
Earnings (loss) per share, Diluted -
Income (loss) from continuing operations, per share	0.97	0.80
Income (loss) from discontinued operations, per share	0.00	(0.12)
Total income (loss) per share, Diluted	$ 0.97	$ 0.68
Weighted Average Number of Shares Outstanding:
Basic	44,053	43,731
Diluted	44,312	43,969
Dividends paid per share of common stock	$ 0.380	$ 0.370

Statement of Comprehensive Income Statement - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income (loss) available for common stock	$ 43,197	$ 29,787
Other comprehensive income (loss), net of tax:
Fair value adjustment on derivatives designated as cash flow hedges (net of tax (expense) benefit of $1,117 and $55, respectively)	(1,661)	576
Reclassification adjustments of benefit plan liability (net of tax of $(175))	457	0
Reclassification adjustments of cash flow hedges settled and included in net income (loss) (net of tax (expense) benefit of $(236) and $445, respectively)	468	(742)
Other comprehensive income (loss), net of tax	(736)	(166)
Comprehensive income (loss) available for common stock	42,461	29,621
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Parenthetical Disclosures
Fair value adjustment of derivatives designated as cash flow hedges, (tax) benefit	1,117	55
Reclassification adjustment of benefit and other postretirement plans included in net income, (tax) benefit	(175)	0
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Tax	$ 236	$ (445)

Consolidated Balance Sheets Statement - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Current assets:
Cash and cash equivalents	$ 12,397	$ 15,462	$ 56,132
Restricted cash and equivalents	6,846	7,916	8,960
Accounts receivable, net	168,783	163,698	143,987
Materials, supplies and fuel	64,189	77,643	63,236
Derivative assets, current	1,630	3,236	17,877
Income tax receivable, net	0	0	10,399
Deferred income tax assets, net, current	38,196	77,231	23,710
Regulatory assets, current	23,422	31,125	56,282
Other current assets	28,260	28,795	26,546
Total current assets	343,723	405,106	407,129
Investments	16,545	16,402	16,451
Property, plant and equipment	3,977,704	3,930,772	3,800,011
Less accumulated depreciation and depletion	(1,210,833)	(1,188,023)	(980,944)
Total property, plant and equipment, net	2,766,871	2,742,749	2,819,067
Other assets:
Goodwill	353,396	353,396	353,396
Intangible assets, net	3,565	3,620	3,787
Derivative assets, non-current	0	510	881
Regulatory assets, non-current	181,119	188,268	186,093
Other assets, non-current	21,367	19,420	21,132
Total other assets, non-current	559,447	565,214	565,289
TOTAL ASSETS	3,686,586	3,729,471	3,807,936
Current liabilities:
Accounts payable	82,437	84,422	59,793
Accrued liabilities	140,230	154,389	151,130
Derivative liabilities, current	89,112	96,541	76,389
Accrued income tax, net	1,157	4,936	0
Regulatory liabilities, current	19,020	13,628	35,414
Notes payable	245,000	277,000	225,000
Current maturities of long-term debt	104,637	103,973	8,977
Total current liabilities	681,593	734,889	556,703
Long-term debt, net of current maturities	936,477	938,877	1,272,016
Deferred credits and other liabilities:
Deferred income tax liabilities, net, non-current	367,502	385,908	317,369
Derivative liabilities, non-current	15,237	16,941	43,169
Regulatory liabilities, non-current	126,573	127,656	112,516
Benefit plan liabilities	172,353	167,397	157,623
Other deferred credits and other liabilities	125,958	125,294	123,848
Total deferred credits and other liabilities	807,623	823,196	754,525
Common stock equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 44,482,304; 44,278,189; and 44,151,428 shares, respectively	44,482	44,278	44,151
Additional Paid in Capital	735,000	733,095	725,512
Retained earnings	519,184	492,869	490,114
Treasury stock, at cost – 41,606; 71,782; and 65,015 shares, respectively	(1,549)	(2,245)	(2,041)
Accumulated other comprehensive income (loss)	(36,224)	(35,488)	(33,044)
Total stockholders’ equity	1,260,893	1,232,509	1,224,692
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,686,586	$ 3,729,471	$ 3,807,936

Consolidated Balance Sheets Parantheticals - $ / shares	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Common Stock, Par Per Share	$ 1.00	$ 1.00	$ 1.00
Common Stock, Shares, Issued	44,523,910	44,349,971	44,216,443
Treasury Stock, Shares	41,606	71,782	65,015
Common Stock, Shares Authorized	100,000,000	100,000,000	100,000,000
Common Stock, Shares, Outstanding	44,482,304	44,278,189	44,151,428

Statement of Cash Flows - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Operating activities:

Net income (loss) available for common stock

$ 43,197

$ 29,787

(Income) loss from discontinued operations, net of tax

5,484

Income (loss) from continuing operations

43,197

35,271

Adjustments to reconcile income (loss) from continuing operations to net cash provided by operating activities:

Depreciation, depletion and amortization

34,781

38,559

Deferred financing cost amortization

1,095

2,719

Derivative fair value adjustments

3,673

1,594

Stock compensation

3,778

1,817

Unrealized mark-to-market (gain) loss on interest rate swaps

(7,456)

(12,045)

Deferred income taxes

20,541

18,083

Allowance for funds used during construction - equity

(200)

(277)

Employee benefit plans

5,548

5,246

Other adjustments, net

3,614

2,243

Changes in certain operating assets and liabilities:

Materials, supplies and fuel

18,519

20,828

Accounts receivable, unbilled revenues and other current assets

(9,166)

9,439

Accounts payable and other current liabilities

(13,637)

(42,368)

Regulatory assets

9,463

(776)

Regulatory liabilities

374

18,938

Contributions to defined benefit pension plans

(25,000)

Other operating activities, net

(4,892)

610

Net cash provided by operating activities of continuing operations

109,232

74,881

Net cash provided by (used in) operating activities of discontinued operations

21,184

Net cash provided by operating activities

109,232

96,065

Investing activities:

Property, plant and equipment additions

(63,939)

(67,652)

Other investing activities

1,030

1,105

Net cash provided by (used in) investing activities of continuing operations

(62,909)

(66,547)

Proceeds from sale of discontinued business operations

108,837

Net cash provided by (used in) investing activities of discontinued operations

(824)

Net cash provided by (used in) investing activities

(62,909)

41,466

Financing activities:

Dividends paid on common stock

(16,882)

(16,276)

Common stock issued

1,231

764

Short-term borrowings - issuances

78,500

56,453

Short-term borrowings - repayments

(110,500)

(176,453)

Long-term debt - repayments

(1,737)

(1,897)

Other financing activities

(2,758)

Net cash provided by (used in) financing activities of continuing operations

(49,388)

(140,167)

Net cash provided by (used in) financing activities of discontinued operations

Net cash provided by (used in) financing activities

(49,388)

(140,167)

Net change in cash and cash equivalents

(3,065)

(2,636)

Cash and Cash Equivalents:

Cash and cash equivalents, beginning of period

15,462

58,768

^[1]

Cash and cash equivalents, end of period

$ 12,397

$ 56,132

[1]	Includes cash of discontinued operations of $37.1 million at Dec. 31, 2011.

Management's Statement	3 Months Ended
Management's Statement	Mar. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Statement [Text Block]	MANAGEMENT'S STATEMENT The unaudited Condensed Consolidated Financial Statements included herein have been prepared by Black Hills Corporation (together with our subsidiaries the “Company,” “us,” “we,” or “our”), 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 Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2012 Annual Report on Form 10-K filed with the SEC. We conduct our operations through the following reportable segments: Electric Utilities, Gas Utilities, Power Generation, Coal Mining and Oil and Gas. 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. All of our operations and assets are located within the United States. Accounting methods historically employed require certain estimates as of interim dates. The information furnished in the accompanying Condensed Consolidated Financial Statements reflects all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the March 31, 2013, Dec. 31, 2012 and March 31, 2012 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 electric utilities is June through August while 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 months ended March 31, 2013 and March 31, 2012, and our financial condition as of March 31, 2013, Dec. 31, 2012, and March 31, 2012 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. On Feb. 29, 2012, we sold our Energy Marketing segment, which resulted in this segment being classified as discontinued operations.

Recently Adopted and Recently Issued Accounting Standards	3 Months Ended
	Mar. 31, 2013
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted and Recently Issued Accounting Pronouncements [Text Block]	RECENTLY ADOPTED AND RECENTLY ISSUED ACCOUNTING STANDARDS AND LEGISLATION Recently Adopted Accounting Standards Reporting of Amounts Reclassified out of Accumulated Other Comprehensive Income, ASU 2013-02 In February 2013, the FASB issued ASU 2013-02 which requires new disclosures for items reclassified out of AOCI. ASU 2013-02 requires disclosure of (1) changes in components of other comprehensive income, (2) for items reclassified out of AOCI and into net income in their entirety, the effect of the reclassification on each affected net income line item and (3) cross references to other disclosures that provide additional detail for components of other comprehensive income that are not reclassified in their entirety to net income. Disclosures are required either on the face of the statements of income or as a separate disclosure in the notes to the financial statements. The new disclosure requirements are effective for interim and annual periods beginning after Dec. 15, 2012. The adoption of this standard did not have an impact on our financial position, results of operations or cash flows. See additional disclosures in Note 8. Balance Sheet: Disclosure about Offsetting Assets and Liabilities, ASU 2011-11 In December 2011, the FASB issued revised accounting guidance to amend disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting and/or similar arrangement. In addition, the revised guidance requires that certain enhanced quantitative and qualitative disclosures are made with respect to a company’s netting arrangements and/or rights of offset associated with its financial instruments and/or derivative instruments. The revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning Jan. 1, 2013. The adoption of this standard did not have an impact on our financial position, results of operations or cash flows. See additional disclosures in Note 12. Recently Issued Accounting Pronouncements and Legislation Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date, ASU 2013-04 In March 2013, the FASB issued new disclosure requirements for recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements including disclosure of the nature and amount of the obligations. The new disclosure requirements are effective for interim and annual periods beginning after Dec. 15, 2013. The amendment requires additional details in the notes to financial statements, but will not have any other impact on our financial statements. Dodd-Frank Wall Street Reform and Consumer Protection Act, SEC Final Rule No. 34-67716 In Aug. 2012, under Dodd-Frank, the SEC adopted new requirements for companies that manufacture or contract to manufacture products that contain certain minerals and metals, known as conflict minerals. The final rules requires all issuers that file reports with the SEC to report supply chain and sourcing information for companies that use conflict minerals on an annual basis. These new requirements will require due diligence efforts in fiscal 2013, with initial disclosure requirements beginning in May 2014. Based on our preliminary analysis, we do not believe that our products contain conflict minerals as defined by the rule; however, our assessment process to determine whether conflict minerals are necessary to the functionality or production of any of our products is not complete.

Supplemental Cash Flow Information

3 Months Ended

Mar. 31, 2013

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosure of Cash Flows [Text Block]

SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION



	Three Months Ended
	March 31, 2013			March 31, 2012
	(in thousands)
Non-cash investing and financing activities from continuing operations—
Property, plant and equipment acquired with accrued liabilities	$	31,780		$	31,644
Increase (decrease) in capitalized assets associated with asset retirement obligations	$	—		$	2,826

Cash (paid) refunded during the period for continuing operations—
Interest (net of amounts capitalized)	$	(12,768	)	$	(16,799	)
Income taxes, net	$	(4,656	)	$	(1,838	)

Materials, Supplies and Fuel

3 Months Ended

Mar. 31, 2013

Inventory, Net [Abstract]

Inventory Disclosure [Text Block]

MATERIALS, SUPPLIES AND FUEL

The following amounts by major classification are included in Materials, supplies and fuel in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2013		Dec. 31, 2012		March 31, 2012
Materials and supplies	$	50,401	$	43,397	$	44,361
Fuel - Electric Utilities	8,445		8,589		7,812
Natural gas in storage held for distribution	5,343		25,657		11,063
Total materials, supplies and fuel	$	64,189	$	77,643	$	63,236

Accounts Receivable and Allowance for Doubtful Accounts

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Accounts Receivable [Text Block]

ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS

Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	Accounts		Unbilled		Less Allowance for			Accounts
March 31, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	47,896	$	21,591	$	(623	)	$	68,864
Gas Utilities	59,024		28,439		(751		)	86,712
Power Generation	3		—		—			3
Coal Mining	1,857		—		—			1,857
Oil and Gas	10,340		—		(19		)	10,321
Corporate	1,026		—		—			1,026
Total	$	120,146	$	50,030	$	(1,393	)	$	168,783



	Accounts		Unbilled		Less Allowance for			Accounts
Dec. 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	54,482	$	23,843	$	(527	)	$	77,798
Gas Utilities	31,495		39,962		(222		)	71,235
Power Generation	16		—		—			16
Coal Mining	2,247		—		—			2,247
Oil and Gas	11,622		—		(19		)	11,603
Corporate	799		—		—			799
Total	$	100,661	$	63,805	$	(768	)	$	163,698



	Accounts		Unbilled		Less Allowance for			Accounts
March 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	44,356	$	19,381	$	(585	)	$	63,152
Gas Utilities	44,287		18,502		(936		)	61,853
Power Generation	265		—		—			265
Coal Mining	2,578		—		—			2,578
Oil and Gas	15,014		—		(105		)	14,909
Corporate	1,230		—		—			1,230
Total	$	107,730	$	37,883	$	(1,626	)	$	143,987

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References

Reference 1: 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=7512638&loc=d3e5066-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3,4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5162-111524

Reference 4: 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 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5074-111524

Reference 6: 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 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 3, 4
-Article 5

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 7
-Article 9

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph k
-Article 4

+ Details

Notes Payable

3 Months Ended

Mar. 31, 2013

Notes Payable [Abstract]

Notes Payable [Text Block]

NOTES PAYABLE

Our Revolving Credit Facility and debt securities contain certain restrictive financial covenants. As of March 31, 2013, we were in compliance with all of these covenants.

We had the following short-term debt outstanding in the Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2013				Dec. 31, 2012				March 31, 2012
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	95,000	$	36,500	$	127,000	$	36,300	$	75,000	$	41,200
Term Loan due June 2013	150,000		—		150,000		—		150,000		—
Total	$	245,000	$	36,500	$	277,000	$	36,300	$	225,000	$	41,200

Debt Covenants

Certain debt obligations require compliance with the following covenants at the end of each quarter (dollars in thousands):



	As of
	March 31, 2013			Covenant Requirement
Consolidated Net Worth	$	1,260,893		Greater than	$	946,493
Recourse Leverage Ratio	52.2		%	Less than	65.0		%

Earnings Per Share

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Earnings Per Share [Text Block]

EARNINGS PER SHARE

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



	Three Months Ended March 31,
	2013		2012

Income (loss) from continuing operations	$	43,197	$	35,271

Weighted average shares - basic	44,053		43,731
Dilutive effect of:
Restricted stock	155		147
Stock options	13		18
Other dilutive effects	91		73
Weighted average shares - diluted	44,312		43,969

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 March 31,
	2013	2012
Stock options	6	127
Restricted stock	34	31
Other stock	—	16
Anti-dilutive shares	40	174

Other Comprehensive Income

3 Months Ended

Mar. 31, 2013

Other Comprehensive Income (Loss), Net of Tax [Abstract]

Comprehensive Income (Loss) Note [Text Block]

OTHER COMPREHENSIVE INCOME

The components of the reclassification adjustments for the period, net of tax, included in Other Comprehensive Income were as follows (in thousands):



	Location on the Condensed Consolidated Statements of Income	Amount Reclassified from AOCI
	Location on the Condensed Consolidated Statements of Income	Three Months Ended March 31, 2013			Three Months Ended March 31, 2012
Gains and losses on cash flow hedges:
Interest rate swaps	Interest expense	$	1,796		$	1,822
Commodity contracts	Revenue	(1,092		)	(3,009		)
		704			(1,187		)
Income tax	Income tax benefit (expense)	(236		)	445
Total reclassification adjustments related to cash flow hedges, net of tax		$	468		$	(742	)

Amortization of defined benefit plans:
Prior service cost	Utilities - Operations and maintenance	$	(31	)	$	—
	Non-regulated energy operations and maintenance	(32		)	—

Actuarial gain (loss)	Utilities - Operations and maintenance	421			—
	Non-regulated energy operations and maintenance	274			—
		632			—
Income tax	Income tax benefit (expense)	(175		)	—
Total reclassification adjustments related to defined benefit plans, net of tax		$	457		$	—

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



	Derivatives Designated as Cash Flow Hedges			Employee Benefit Plans			Total
Balance as of December 31, 2011	$	(13,802	)	$	(19,076	)	$	(32,878	)
Other comprehensive income (loss), net of tax	(166		)	—			(166		)
Ending Balance March 31, 2012	$	(13,968	)	$	(19,076	)	$	(33,044	)

Balance as of December 31, 2012	$	(15,713	)	$	(19,775	)	$	(35,488	)
Other comprehensive income (loss), net of tax	(1,193		)	457			(736		)
Ending Balance March 31, 2013	$	(16,906	)	$	(19,318	)	$	(36,224	)

- Definition

The entire disclosure for any adjustments made during the period to avoid double counting in comprehensive income items displayed as part of net income that also had been displayed as part of other comprehensive income in that period or earlier periods. These adjustments include reclassifications to net income of items in accumulated comprehensive income, such as deferred gains or losses on qualifying hedges when hedged item reported in net income, holding gains or losses on available-for-sale securities transferred into trading category, unrealized holding gains or losses on debt securities transferred from held-to-maturity category into available-for-sale category and accumulated translation adjustment attributable to foreign subsidiary or investment in foreign entity upon sale or liquidation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

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-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
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-Paragraph 10
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 31
-Article 5

+ Details

Employee Benefit Plans

3 Months Ended

Mar. 31, 2013

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Pension and Other Postretirement Benefits Disclosure [Text Block]

EMPLOYEE BENEFIT PLANS

Defined Benefit Pension Plans

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



	Three Months Ended March 31,
	2013			2012
Service cost	$	1,608		$	1,430
Interest cost	3,825			3,687
Expected return on plan assets	(4,654		)	(4,084		)
Prior service cost	16			22
Net loss (gain)	3,062			2,408
Net periodic benefit cost	$	3,857		$	3,463

Non-pension Defined Benefit Postretirement Healthcare Plans

The components of net periodic benefit cost for the Non-pension Defined Benefit Postretirement Healthcare Plans were as follows (in thousands):



	Three Months Ended March 31,
	2013			2012
Service cost	$	419		$	402
Interest cost	417			523
Expected return on plan assets	(20		)	(19		)
Prior service cost (benefit)	(125		)	(125		)
Net loss (gain)	121			222
Net periodic benefit cost	$	812		$	1,003

Supplemental Non-qualified Defined Benefit and Defined Contribution Plans

The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit and Defined Contribution Plans were as follows (in thousands):



	Three Months Ended March 31,
	2013		2012
Service cost	$	348	$	246
Interest cost	332		331
Prior service cost	1		1
Net loss (gain)	198		202
Net periodic benefit cost	$	879	$	780

Contributions

We anticipate that we will make contributions to the benefit plans during 2013 and 2014. Contributions to the Pension Plans are cash contributions made directly to the Pension Plan Trust accounts. Healthcare and Supplemental Plan contributions are made in the form of benefit payments. Contributions and anticipated contributions are as follows (in thousands):



	Contributions Made		Additional
	Three Months Ended March 31, 2013		Contributions Anticipated for 2013		Contributions Anticipated for 2014
Defined Benefit Pension Plans	$	—	$	8,787	$	19,922
Non-pension Defined Benefit Postretirement Healthcare Plans	$	784	$	2,352	$	3,350
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	322	$	965	$	1,463

- Definition

The entire disclosure for pension and other postretirement benefits.

+ References

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Reference 14: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Business Segment Information

3 Months Ended

Mar. 31, 2013

Segment Reporting Information, Additional Information [Abstract]

Segment Reporting Disclosure [Text Block]

BUSINESS SEGMENT INFORMATION

Segment information and Corporate activities included in the accompanying Condensed Consolidated Statements of Income and Condensed Consolidated Balance Sheets are below.

On Feb. 29, 2012, we sold our Energy Marketing segment, Enserco, which resulted in this segment being classified as discontinued operations. Indirect corporate costs and inter-segment interest expense related to Enserco that have not been classified as discontinued operations have been reclassified to Corporate activity.

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



Three Months Ended March 31, 2013	External Operating Revenue		Intercompany Operating Revenue			Income (Loss) from Continuing Operations
Utilities:
Electric	$	158,483	$	4,147		$	12,356
Gas	199,812		—			18,483
Non-regulated Energy:
Power Generation	1,022		19,338			5,644
Coal Mining	6,010		7,573			1,065
Oil and Gas	15,344		—			(53		)
Corporate activities ^(a)	—		—			5,699
Intercompany eliminations	—		(31,058		)	3
Total	$	380,671	$	—		$	43,197



Three Months Ended March 31, 2012	External Operating Revenue		Intercompany Operating Revenue			Income (Loss) from Continuing Operations
Utilities:
Electric	$	156,133	$	3,036		$	8,746
Gas	180,522		—			15,207
Non-regulated Energy:
Power Generation	1,178		18,449			6,914
Coal Mining	6,373		8,616			1,000
Oil and Gas	21,645		—			13
Corporate activities ^(a)(b)	—		—			3,391
Intercompany eliminations	—		(30,101		)	—
Total	$	365,851	$	—		$	35,271

_____________


(a)	Income (loss) from continuing operations includes a $4.8 million and a $7.8 million net after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 and 2012, respectively.


(b)	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the three months ended March 31, 2012 were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.

Segment information and Corporate balances included in the accompanying Condensed Consolidated Balance Sheets was as follows (in thousands):



Total Assets (net of inter-company eliminations) as of:	March 31, 2013		Dec. 31, 2012		March 31, 2012
Utilities:
Electric ^(a)	$	2,367,014	$	2,387,458	$	2,268,524
Gas	752,468		765,165		717,185
Non-regulated Energy:
Power Generation^(a)	115,708		119,170		128,225
Coal Mining	82,839		83,810		87,139
Oil and Gas	255,786		258,460		430,851
Corporate activities	112,771		115,408		176,012
Total assets	$	3,686,586	$	3,729,471	$	3,807,936

___________


(a)	The PPA under which the Pueblo Airport Generation site owned by Colorado IPP supports Colorado customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total Assets of Electric Utilities Segment under this accounting for a capital lease.

- 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 Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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+ Details

Risk Management Activities

3 Months Ended

Mar. 31, 2013

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Risk Managment 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 credit risk. To manage and mitigate these identified risks, we have adopted the Black Hills Corporation Risk Policies and Procedures as discussed in our 2012 Annual Report on Form 10-K.

Market Risk

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 including, but not limited to:


•	Commodity price risk associated with our natural long position with crude oil and natural gas reserves and production and fuel procurement for certain of our gas-fired generation assets; and


•	Interest rate risk associated with our variable rate credit facility, project financing floating rate debt and our other long-term debt instruments.

Credit Risk

Credit risk is the risk of financial loss resulting from non-performance of contractual obligations by a counterparty.

For production and generation activities, we attempt to mitigate our credit exposure by conducting business primarily with high credit quality entities, setting tenor and credit limits commensurate with counterparty financial strength, obtaining master netting agreements, and mitigating credit exposure with less creditworthy counterparties through parental guarantees, prepayments, letters of credit, and other security agreements.

We perform ongoing credit evaluations of our customers and adjust credit limits based upon payment history and the customer’s current creditworthiness, as determined by review of their current credit information. We maintain a provision for estimated credit losses based upon historical experience and any specific customer collection issue that is identified.

As of March 31, 2013, our credit exposure included a $2.3 million exposure to a non-investment grade energy marketing company. The remainder of our credit exposure was concentrated primarily among retail utility customers, investment grade companies, cooperative utilities and federal agencies. Our derivative and hedging activities included in the accompanying Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Income and Condensed Consolidated Statements of Comprehensive Income (Loss) are detailed below and within Note 12.

Oil and Gas

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.

To mitigate commodity price risk and preserve cash flows, we primarily use over-the-counter swaps, exchange traded futures and related options to hedge portions of our crude oil and natural gas production. We elect hedge accounting on these instruments. These transactions were designated at inception as cash flow hedges, documented under accounting standards 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 were 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 for which we have elected cash flow hedge accounting is reported in AOCI on the accompanying Condensed Consolidated Balance Sheets and the ineffective portion, if any, is reported in Revenue on the accompanying Condensed Consolidated Statements of Income.

We had the following derivatives and related balances for our Oil and Gas segment (dollars in thousands) as of:



	March 31, 2013					Dec. 31, 2012				March 31, 2012
	Crude oil futures, swaps and options		Natural gas futures and swaps			Crude oil futures, swaps and options		Natural gas futures and swaps		Crude oil futures, swaps and options			Natural gas futures and swaps
Notional ^(a)	522,000		10,633,000			528,000		8,215,500		522,000			5,001,750
Maximum terms in years ^(b)	0.75		0.5			1		0.75		1.25			1.5
Derivative assets, current	$	821	$	287		$	1,405	$	1,831	$	406		$	8,256
Derivative assets, non-current	$	—	$	—		$	297	$	170	$	46		$	808
Derivative liabilities, current	$	250	$	1,188		$	847	$	507	$	2,904		$	—
Derivative liabilities, non-current	$	—	$	—		$	—	$	—	$	1,084		$	—
Pre-tax accumulated other comprehensive income (loss)	$	10	$	(2,781	)	$	206	$	873	$	(3,566	)	$	9,064
Cash collateral receivable (payable) included in derivatives	$	730	$	1,880		$	786	$	620	$	—		$	—
Cash collateral included in Other current assets	$	723	$	2,102		$	1,078	$	709	$	—		$	—

____________


(a)	Crude oil in Bbls, natural gas in MMBtus.


(b)	Refers to the term of the derivative instrument. Assets and liabilities are classified as current/non-current based on the term of the hedged transaction and the corresponding settlement of the derivative instrument.

Based on March 31, 2013 market prices, a $0.2 million loss would be reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market prices fluctuate.

Utilities

The operations of our utilities, including tolling arrangements, expose our utility customers to volatility in natural gas prices; therefore, as allowed or required by state utility commissions, we have entered into commission approved hedging programs utilizing natural gas futures, options and basis swaps to reduce our customers’ underlying exposure to these fluctuations. These transactions are considered derivatives and in accordance with accounting standards for derivatives and hedging, mark-to-market adjustments are recorded as Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets. Unrealized and realized gains and losses, as well as option premiums and commissions on these transactions are recorded as Regulatory assets or Regulatory liabilities in accordance with state commission guidelines. Accordingly, the hedging activity is recognized in the Condensed Consolidated Statements of Income or the Condensed Consolidated Statements of Comprehensive Income (Loss) when the related costs are recovered through our rates.

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



	March 31, 2013		Dec. 31, 2012		March 31, 2012
	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)
Natural gas futures purchased	13,180,000	80	15,350,000	83	11,550,000	81
Natural gas options purchased	440,000	5	2,430,000	2	670,000	12
Natural gas basis swaps purchased	11,350,000	69	12,020,000	72	7,640,000	81

We had the following derivative balances related to the hedges in our Utilities (in thousands) as of:



	March 31, 2013		Dec. 31, 2012		March 31, 2012
Derivative assets, current	$	522	$	—	$	9,215
Derivative assets, non-current	$	—	$	43	$	27
Derivative liabilities, non-current	$	—	$	—	$	6,407
Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	4,315	$	9,596	$	15,223

Cash collateral receivable (payable) included in derivatives	$	4,487	$	8,576	$	17,651
Cash collateral included in Other current assets	$	3,295	$	4,354	$	—
Option premiums and commissions included in derivatives	$	350	$	1,063	$	407

Financing Activities

We have entered into floating-to-fixed interest rate swap agreements to reduce our exposure to interest rate fluctuations associated with our floating rate debt obligations. Our interest rate swaps and related balances were as follows (dollars in thousands) as of:



	March 31, 2013						Dec. 31, 2012						March 31, 2012
	Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)			Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)			Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)
Notional	$	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	3.75			0.75			4.00			1.00			4.75			1.75
Derivative liabilities, current	$	6,982		$	80,692		$	7,039		$	88,148		$	6,777		$	66,708
Derivative liabilities, non-current	$	15,237		$	—		$	16,941		$	—		$	18,441		$	17,237
Pre-tax accumulated other comprehensive income (loss)	$	(22,219	)	$	—		$	(23,980	)	$	—		$	(25,218	)	$	—
Pre-tax gain (loss)	$	—		$	7,456		$	—		$	1,882		$	—		$	12,045
Cash collateral receivable (payable) included in derivatives	$	—		$	5,960		$	—		$	5,960		$	—		$	—

_____________

(a)

These swaps have been designated to $75.0 million of borrowings on our Revolving Credit Facility and $75.0 million of borrowings on our project financing debt at Black Hills Wyoming. The swaps transferred to Black Hills Wyoming such that BHC and Black Hills Wyoming are both jointly and severally liable for the amount of those obligations. These swaps are priced using three-month LIBOR, matching the floating portion of the related swaps.


(b)	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in 6 years and de-designated swaps totaling $150.0 million notional terminate in 16 years.

Collateral requirements based on our corporate credit rating apply to $50.0 million of our de-designated swaps. At our current credit ratings, we are required to post collateral for any amount by which the swaps’ negative mark-to-market fair value exceeds $20.0 million. If our senior unsecured credit rating drops to BB+ or below by S&P, or to Ba1 or below by Moody’s, we would be required to post collateral for the entire amount of the swaps’ negative mark-to-market fair value. We had $6.0 million cash collateral posted at March 31, 2013.

Based on March 31, 2013 market interest rates and balances related to our designated interest rate swaps, a loss of approximately $7.0 million would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market interest rates change.

- 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

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+ Details

Fair Value Measurements

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Derivatives and Fair Value [Text Block]

FAIR VALUE MEASUREMENTS

Derivative Financial Instruments

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. We record transfers, if necessary, between levels at the end of the reporting period for all of our financial instruments. For additional information see Notes 1, 3 and 4 included in our 2012 Annual Report on Form 10-K filed with the SEC.

Transfers into Level 3, if any, occur when significant inputs used to value the derivative instruments become less observable such as a significant decrease in the frequency and volume in which the instrument is traded, negatively impacting the availability of observable pricing inputs. Transfers out of Level 3, if any, occur when the significant inputs become more observable such as the time between the valuation date and the delivery date of a transaction becomes shorter, positively impacting the availability of observable pricing inputs.

Valuation Methodologies for Derivatives

Oil and Gas Segment:


•	The commodity option contracts for our Oil and Gas segment are valued under the market approach and include calls and puts. Fair value was derived using quoted prices from third party brokers for similar instruments as to quantity and timing. The prices are then validated through third party sources and therefore support Level 2 disclosure.


•	The commodity basis swaps for our Oil and Gas segment are valued under the market approach using the instrument’s current forward price strip hedged for the same quantity and date and discounted based on the three-month LIBOR. We utilize observable inputs which support Level 2 disclosure.

Utilities Segment:

•

The commodity contracts for our Utilities, valued using the market approach, include exchange-traded futures, options and basis swaps (Level 2) and OTC basis swaps (Level 3) for natural gas contracts. For Level 2 assets and liabilities, fair value was derived using broker quotes validated by the Chicago Mercantile Exchange pricing for similar instruments. For Level 3 assets and liabilities, fair value was derived using average price quotes from the OTC contract broker and an independent third party market participant since these instruments are not traded on an exchange.

Corporate Activities:

•

The interest rate swaps are valued using the market approach. We establish fair value by obtaining price quotes directly from the counterparty which are based on the floating three-month LIBOR curve for the term of the contract. The fair value obtained from the counterparty is then validated by utilizing a nationally recognized service that obtains observable inputs to compute fair value for the same instrument. In addition, the fair value for the interest rate swap derivatives includes a CVA component. The CVA considers the fair value of the interest rate swap and the probability of default based on the life of the contract. For the probability of a default component, we utilize observable inputs supporting Level 2 disclosure by using our credit default spread, if available, or a generic credit default spread curve that takes into account our credit ratings.

Recurring Fair Value Measurements

There have been no significant transfers between Level 1 and Level 2 derivative balances. 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 March 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	71	$	—	$	(11	)	$	60
Basis Swaps -- Oil	—		836		—		(75		)	761
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		435		—		(148		)	287
Commodity derivatives — Utilities	—		1,897		—		(1,375		)	522
Cash equivalents ^(a)	12,397		—		—		—			12,397
Total	$	12,397	$	3,239	$	—	$	(1,609	)	$	14,027

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	396	$	—	$	(204	)	$	192
Basis Swaps -- Oil	—		670		—		(612		)	58
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		3,216		—		(2,028		)	1,188
Commodity derivatives — Utilities	—		5,862		—		(5,862		)	—
Interest rate swaps	—		108,871		—		(5,960		)	102,911
Total	$	—	$	119,015	$	—	$	(14,666	)	$	104,349

______________


(a)	Level 1 assets and liabilities are described in Note 13.



	As of Dec. 31, 2012
	Level 1		Level 2		Level 3			Cash Collateral and Counterparty Netting			Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	378	$	—		$	—		$	378
Basis Swaps -- Oil	—		1,325		—			—			1,325
Options -- Gas	—		—		—			—			—
Basis Swaps -- Gas	—		2,000		—			—			2,000
Commodity derivatives —Utilities	—		—		43		^(b)	—			43
Cash equivalents ^(a)	15,462		—		—			—			15,462
Total	$	15,462	$	3,703	$	43		$	—		$	19,208

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	1,131	$	—		$	(336	)	$	795
Basis Swaps -- Oil	—		502		—			(450		)	52
Options -- Gas	—		—		—			—			—
Basis Swaps -- Gas	—		1,127		—			(620		)	507
Commodity derivatives — Utilities	—		10,162		—			(10,162		)	—
Interest rate swaps	—		118,088		—			(5,960		)	112,128
Total	$	—	$	131,010	$	—		$	(17,528	)	$	113,482

______________


(a)	Level 1 assets and liabilities are described in Note 13.

(b)

The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.



	As of March 31, 2012
	Level 1		Level 2			Level 3			Cash Collateral and Counterparty Netting		Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	404		$	—		$	—	$	404
Basis Swaps -- Oil	—		48			—			—		48
Options -- Gas	—		—			—			—		—
Basis Swaps -- Gas	—		9,064			—			—		9,064
Commodity derivatives — Utilities	—		(8,412		)	3		^(b)	17,651		9,242
Cash equivalents ^(a)	55,919		—			—			—		55,919
Total	$	55,919	$	1,104		$	3		$	17,651	$	74,677

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	1,347		$	—		$	—	$	1,347
Basis Swaps -- Oil	—		2,641			—			—		2,641
Options -- Gas	—		—			—			—		—
Basis Swaps -- Gas	—		—			—			—		—
Commodity derivatives — Utilities	—		6,359			48		^(b)	—		6,407
Interest rate swaps	—		109,163			—			—		109,163
Total	$	—	$	119,510		$	48		$	—	$	119,558

______________


(a)	Level 1 assets and liabilities are described in Note 13.

(b)

Fair Value Measures By Balance Sheet Classification

As required by accounting standards for derivatives and hedges, fair values within the following tables are presented on a gross basis and reflect the netting of asset and liability positions permitted in accordance with accounting standards for offsetting and under terms of our master netting agreements and the amounts do not include net cash collateral on deposit in margin accounts at March 31, 2013, Dec. 31, 2012, and March 31, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the 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 11.

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



As of March 31, 2013
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	832	$	—
Commodity derivatives	Derivative assets — non-current	206		—
Commodity derivatives	Derivative liabilities — current	—		3,110
Commodity derivatives	Derivative liabilities — non-current	—		1,114
Interest rate swaps	Derivative liabilities — current	—		6,982
Interest rate swaps	Derivative liabilities — non-current	—		15,237
Total derivatives designated as hedges		$	1,038	$	26,443

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,201	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		58
Commodity derivatives	Derivative liabilities — non-current	—		5,862
Interest rate swaps	Derivative liabilities — current	—		86,652
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	2,201	$	92,572



As of Dec. 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,874	$	—
Commodity derivatives	Derivative assets — non-current	510		—
Commodity derivatives	Derivative liabilities — current	—		1,993
Commodity derivatives	Derivative liabilities — non-current	—		821
Interest rate swaps	Derivative liabilities — current	—		7,038
Interest rate swaps	Derivative liabilities — non-current	—		16,941
Total derivatives designated as hedges		$	3,384	$	26,793

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	362	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	1,180		4,957
Commodity derivatives	Derivative liabilities — non-current	406		5,153
Interest rate swaps	Derivative liabilities — current	—		94,108
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	1,948	$	104,218



As of March 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	8,662	$	—
Commodity derivatives	Derivative assets — non-current	854		—
Commodity derivatives	Derivative liabilities — current	—		2,904
Commodity derivatives	Derivative liabilities — non-current	—		1,084
Interest rate swaps	Derivative liabilities — current	—		6,777
Interest rate swaps	Derivative liabilities — non-current	—		18,441
Total derivatives designated as hedges		$	9,516	$	29,206

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	—	$	8,436
Commodity derivatives	Derivative assets — non-current	—		(27		)
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		6,407
Interest rate swaps	Derivative liabilities — current	—		66,708
Interest rate swaps	Derivative liabilities — non-current	—		17,237
Total derivatives not designated as hedges		$	—	$	98,761

Derivatives Offsetting

It is our policy to offset in our Condensed Consolidated Balance Sheets contracts which provide for legally enforceable netting for our accounts receivable and payable and derivative activities. The tables below do not reflect accounts receivable or accounts payable subject to master netting agreements.

As required by accounting standards for derivatives and hedges, fair values within the following tables are presented on a gross basis and reflect the netting of asset and liability positions permitted in accordance with accounting standards for offsetting and under the terms of our master netting agreements. Additionally, the amounts reflect cash collateral on deposit in margin accounts at March 31, 2013, Dec. 31, 2012, and March 31, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the gross balances are not indicative of either our actual credit exposure or net economic exposure.

Offsetting of derivative assets and derivative liabilities as of March 31, 2013 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	75	$	—		$	(75	)	$	—
Oil and Gas - Crude Options	11		—			(11		)	—
Oil and Gas - Natural Gas Basis Swaps	148		—			(148		)	—
Utilities	1,897		(1,375		)	—			522
Total derivative assets subject to a master netting agreement or similar arrangement	2,131		(1,375		)	(234		)	522

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	761		—			—			761
Oil and Gas - Crude Options	60		—			—			60
Oil and Gas - Natural Gas Basis Swaps	287		—			—			287
Utilities	—		—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	1,108		—			—			1,108

Total derivative assets	$	3,239	$	(1,375	)	$	(234	)	$	1,630



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	612	$	—		$	(612	)	$	—
Oil and Gas - Crude Options	204		—			(204		)	—
Oil and Gas - Natural Gas Basis Swaps	2,028		—			(2,028		)	—
Utilities	5,862		(1,375		)	(4,487		)	—
Interest Rate Swaps	—		—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	8,706		(1,375		)	(7,331		)	—

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	58		—			—			58
Oil and Gas - Crude Options	192		—			—			192
Oil and Gas - Natural Gas Basis Swaps	1,188		—			—			1,188
Utilities	—		—			—			—
Interest Rate Swaps	108,871		—			(5,960		)	102,911
Total derivative liabilities not subject to a master netting agreement or similar arrangement	110,309		—			(5,960		)	104,349

Total derivative liabilities	$	119,015	$	(1,375	)	$	(13,291	)	$	104,349

Offsetting of derivative assets and derivative liabilities as of Dec. 31, 2012 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives		Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	76	$	—		$	—	$	76
Oil and Gas - Crude Options	93		—			—		93
Oil and Gas - Natural Gas Basis Swaps	172		—			—		172
Utilities	1,629		(1,586		)	—		43
Total derivative assets subject to a master netting agreement or similar arrangement	1,970		(1,586		)	—		384

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,249		—			—		1,249
Oil and Gas - Crude Options	285		—			—		285
Oil and Gas - Natural Gas Basis Swaps	1,828		—			—		1,828
Utilities	—		—			—		—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,362		—			—		3,362

Total derivative assets	$	5,332	$	(1,586	)	$	—	$	3,746



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	449	$	—		$	(449	)	$	—
Oil and Gas - Crude Options	337		—			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620		—			(620		)	—
Utilities	10,162		(1,586		)	(8,576		)	—
Interest Rate Swaps	—		—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568		(1,586		)	(9,982		)	—

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52		—			—			52
Oil and Gas - Crude Options	795		—			—			795
Oil and Gas - Natural Gas Basis Swaps	507		—			—			507
Utilities	—		—			—			—
Interest Rate Swaps	118,088		—			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442		—			(5,960		)	113,482

Total derivative liabilities	$	131,010	$	(1,586	)	$	(15,942	)	$	113,482

Offsetting of derivative assets and derivative liabilities as of March 31, 2012 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets		Cash Collateral included in Derivatives		Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—	$	—	$	—
Oil and Gas - Crude Options	—			—		—		—
Oil and Gas - Natural Gas Basis Swaps	—			—		—		—
Utilities	(8,409		)	—		17,651		9,242
Total derivative assets subject to a master netting agreement or similar arrangement	(8,409		)	—		17,651		9,242

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	48			—		—		48
Oil and Gas - Crude Options	404			—		—		404
Oil and Gas - Natural Gas Basis Swaps	9,064			—		—		9,064
Utilities	—			—		—		—
Total derivative assets not subject to a master netting agreement or similar arrangement	9,516			—		—		9,516

Total derivative assets	$	1,107		$	—	$	17,651	$	18,758



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets		Cash Collateral included in Derivatives		Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—	$	—	$	—	$	—
Oil and Gas - Crude Options	—		—		—		—
Oil and Gas - Natural Gas Basis Swaps	—		—		—		—
Utilities	6,407		—		—		6,407
Interest Rate Swaps	—		—		—		—
Total derivative liabilities subject to a master netting agreement or similar arrangement	6,407		—		—		6,407

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	2,641		—		—		2,641
Oil and Gas - Crude Options	1,347		—		—		1,347
Oil and Gas - Natural Gas Basis Swaps	—		—		—		—
Utilities	—		—		—		—
Interest Rate Swaps	109,163		—		—		109,163
Total derivative liabilities not subject to a master netting agreement or similar arrangement	113,151		—		—		113,151

Total derivative liabilities	$	119,558	$	—	$	—	$	119,558

Derivative assets and derivative liabilities and collateral held by counterparty as of March 31, 2013 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	1,108		—		1,108
Utilities	Counterparty A	522		—		522
		$	1,630	$	—	$	1,630



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—	$	(2,825	)	$	(2,825	)
Oil and Gas	Counterparty B	1,438		—			1,438
Utilities	Counterparty A	—		(3,295		)	(3,295		)
Interest Rate Swap	Counterparty D	4,266		—			4,266
Interest Rate Swap	Counterparty E	26,754		—			26,754
Interest Rate Swap	Counterparty F	11,841		—			11,841
Interest Rate Swap	Counterparty G	24,905		—			24,905
Interest Rate Swap	Counterparty H	14,625		—			14,625
Interest Rate Swap	Counterparty I	20,520		—			20,520
		$	104,349	$	(6,120	)	$	98,229

Derivative assets and derivative liabilities and collateral held by counterparty as of Dec. 31, 2012 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	341	$	—	$	341
Oil and Gas	Counterparty B	3,362		—		3,362
Utilities	Counterparty A	43		—		43
		$	3,746	$	—	$	3,746



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—	$	(1,787	)	$	(1,787	)
Oil and Gas	Counterparty B	1,354		—			1,354
Utilities	Counterparty A	—		(4,354		)	(4,354		)
Interest Rate Swap	Counterparty D	4,588		—			4,588
Interest Rate Swap	Counterparty E	29,245		—			29,245
Interest Rate Swap	Counterparty F	12,721		—			12,721
Interest Rate Swap	Counterparty G	26,520		—			26,520
Interest Rate Swap	Counterparty H	16,809		—			16,809
Interest Rate Swap	Counterparty I	22,245		—			22,245
		$	113,482	$	(6,141	)	$	107,341

Derivative assets and derivative liabilities and collateral held by counterparty as of March 31, 2012 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	9,516		—		9,516
Utilities	Counterparty A	9,242		—		9,242
		$	18,758	$	—	$	18,758



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid		Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	3,988		—		3,988
Utilities	Counterparty A	6,407		—		6,407
Interest Rate Swap	Counterparty D	4,810		—		4,810
Interest Rate Swap	Counterparty E	27,137		—		27,137
Interest Rate Swap	Counterparty F	13,027		—		13,027
Interest Rate Swap	Counterparty G	24,617		—		24,617
Interest Rate Swap	Counterparty H	19,808		—		19,808
Interest Rate Swap	Counterparty I	19,764		—		19,764
		$	119,558	$	—	$	119,558

A description of our derivative activities is included in Note 11. The following tables present the impact that derivatives had on our Condensed Consolidated Statements of Income.

Cash Flow Hedges

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



Three Months Ended March 31, 2013
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	$	(19	)	Interest expense	$	(1,796	)		$	—
Commodity derivatives	(2,759		)	Revenue	1,092				—
Total	$	(2,778	)		$	(704	)		$	—



Three Months Ended March 31, 2012
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	$	(762	)	Interest expense	$	(1,822	)		$	—
Commodity derivatives	1,283			Revenue	3,009				—
Total	$	521			$	1,187			$	—

Derivatives Not Designated as Hedge Instruments

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



		Three Months Ended
		March 31, 2013
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income
Interest rate swaps - unrealized	Unrealized gain (loss) on interest rate swaps, net	$	7,456
Interest rate swaps - realized	Interest expense	(3,427		)
		$	4,029



		Three Months Ended
		March 31, 2012
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income
Interest rate swaps - unrealized	Unrealized gain (loss) on interest rate swaps, net	$	12,045
Interest rate swaps - realized	Interest expense	(3,205		)
		$	8,840

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2013

Fair Value of Financial Instruments [Abstract]

Fair Value Disclosures [Text Block]

FAIR VALUE OF FINANCIAL INSTRUMENTS

The estimated fair values of our financial instruments are as follows (in thousands) as of:



	March 31, 2013				Dec. 31, 2012				March 31, 2012
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents ^(a)	$	12,397	$	12,397	$	15,462	$	15,462	$	56,132	$	56,132
Restricted cash and equivalents ^(a)	$	6,846	$	6,846	$	7,916	$	7,916	$	8,960	$	8,960
Notes payable ^(a)	$	245,000	$	245,000	$	277,000	$	277,000	$	225,000	$	225,000
Long-term debt, including current maturities ^(b)	$	1,041,114	$	1,208,909	$	1,042,850	$	1,231,559	$	1,280,993	$	1,439,724

____________


(a)	Fair value approximates carrying value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates and therefore is classified in Level 1 in the fair value hierarchy.


(b)	Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

- 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 Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Number 107
-Paragraph 15B
-Subparagraph a, b
-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
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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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.

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-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 11: http://www.xbrl.org/2003/role/presentationRef
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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 12: http://www.xbrl.org/2003/role/presentationRef
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-Paragraph 32, 33, 34
-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 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-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.

+ Details

Commitments and Contingencies

3 Months Ended

Mar. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies Disclosure [Text Block]

COMMITMENTS AND CONTINGENCIES

Commitments and Contingencies

There have been no significant changes to commitments and contingencies, other than those described below, from those previously disclosed in Note 19 of our Notes to the Consolidated Financial Statements in our 2012 Annual Report on Form 10-K.

The following purchase power and power sales agreements were renewed during the first quarter of 2013:


•	Cheyenne Light renewed an agreement with Basin Electric whereby Cheyenne Light will receive 40 megawatts of capacity and energy from Basin Electric through Sept. 30, 2014. This agreement is subject to FERC approval which is expected during the second quarter of 2013.


•	Cheyenne Light renewed an agreement with Basin Electric whereby Cheyenne Light provides 40 megawatts of capacity and energy through Sept. 30, 2014. This agreement is subject to FERC approval which is expected during the second quarter of 2013.

Other Commitments

Construction of Cheyenne Prairie, a 132 megawatt natural gas-fired electric generating facility, by Cheyenne Light and Black Hills Power is expected to cost approximately $222.0 million, exclusive of financing costs. Construction is expected to be completed by Sept. 30, 2014. As of March 31, 2013, committed contracts for equipment purchases and for construction were 28 percent and 13 percent complete, respectively.

Oil Creek Fire

On June 29, 2012, a forest and grassland fire occurred in the western Black Hills. Our utility subsidiary, Black Hills Power, subsequently received written damage claims from the State of Wyoming and one landowner seeking recovery for alleged injury to timber, grass, fencing, fire suppression and rehabilitation costs of approximately $8.0 million. On April 16, 2013, thirty-four private landowners filed suit in United States District Court for the District of Wyoming, asserting similar claims, based upon allegations of negligence, common law nuisance and trespass. The suit seeks recovery of both actual and exemplary damages in an unspecified amount. Our investigation into the cause and origin of the fire is pending. We expect to deny and will vigorously defend all claims arising out of the lawsuit, pending the completion of our investigation. Given the uncertainty of litigation, however, a loss related to the fire and the litigation is reasonably possible. We cannot reasonably estimate the amount of a potential loss because our investigation is ongoing. Further claims may be presented by other parties. Although we cannot predict the outcome of our investigation or the viability of alleged claims, based on information currently available, management believes that any such claims, if determined adversely to us, will not have a material adverse effect on our financial condition or results of operation.

Sale of Enserco Energy Inc.

In December 2012, we agreed to arbitrate certain claims that we believe are properly characterized as purchase price adjustments related to the sale of Enserco, but objected to the arbitration of additional claims that we believe are not properly characterized as purchase price adjustments. After joint discussions of the parties with the arbitrator in January 2013, the arbitrator advised the parties that it would not arbitrate the claims to which we objected. On April 11, 2013, the buyer filed a petition in the Colorado District Court for the City and County of Denver, Colorado, seeking an order compelling arbitration on all of the disputed claims. We responded by requesting the court to deny the buyer’s petition. The filing of this petition does not alter our characterization or evaluation of the original claim.

Dividend Restrictions

Our Revolving Credit Facility and other debt obligations contain restrictions on the payment of cash dividends upon a default or event of default. As of March 31, 2013, 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 at March 31, 2013:


•	Our utilities are generally limited to the amount of dividends allowed to be paid to us as a utility holding company under the Federal Power Act and settlement agreements with state regulatory jurisdictions. As of March 31, 2013, the restricted net assets at our Utilities Group were approximately $205.9 million.


•	As required by the covenant in the Black Hills Wyoming project financing, Black Hills Non-regulated Holdings has maintained restricted shareholders’ equity of at least $100.0 million.

Guarantees

As of Dec. 31, 2012, the Company had provided a guarantee for up to $33.3 million of Colorado Electric’s performance and payment obligations relating to the purchase of wind turbines for the Colorado Electric wind power generation project. The guarantee expired March 29, 2013 upon fulfillment of all contractual obligations.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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+ Details

Supplemental Cash Flow Information Supplmental Cash Flow Information (Tables)

3 Months Ended

Mar. 31, 2013

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosures of Cash Flows [Table Text Block]



	Three Months Ended
	March 31, 2013			March 31, 2012
	(in thousands)
Non-cash investing and financing activities from continuing operations—
Property, plant and equipment acquired with accrued liabilities	$	31,780		$	31,644
Increase (decrease) in capitalized assets associated with asset retirement obligations	$	—		$	2,826

Cash (paid) refunded during the period for continuing operations—
Interest (net of amounts capitalized)	$	(12,768	)	$	(16,799	)
Income taxes, net	$	(4,656	)	$	(1,838	)

Materials, Supplies and Fuel Materials, Supplies and Fuel (Tables)

3 Months Ended

Mar. 31, 2013

Inventory, Net [Abstract]

Schedule of Inventory, Current [Table Text Block]

The following amounts by major classification are included in Materials, supplies and fuel in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2013		Dec. 31, 2012		March 31, 2012
Materials and supplies	$	50,401	$	43,397	$	44,361
Fuel - Electric Utilities	8,445		8,589		7,812
Natural gas in storage held for distribution	5,343		25,657		11,063
Total materials, supplies and fuel	$	64,189	$	77,643	$	63,236

Accounts Receivable and Allowance for Doubtful Accounts Accounts Receivable and Allowance for Doubtful Accounts (Tables)

3 Months Ended

Mar. 31, 2013

Receivables [Abstract]

Schedule of Accounts Receivable [Table Text Block]

Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	Accounts		Unbilled		Less Allowance for			Accounts
March 31, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	47,896	$	21,591	$	(623	)	$	68,864
Gas Utilities	59,024		28,439		(751		)	86,712
Power Generation	3		—		—			3
Coal Mining	1,857		—		—			1,857
Oil and Gas	10,340		—		(19		)	10,321
Corporate	1,026		—		—			1,026
Total	$	120,146	$	50,030	$	(1,393	)	$	168,783



	Accounts		Unbilled		Less Allowance for			Accounts
Dec. 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	54,482	$	23,843	$	(527	)	$	77,798
Gas Utilities	31,495		39,962		(222		)	71,235
Power Generation	16		—		—			16
Coal Mining	2,247		—		—			2,247
Oil and Gas	11,622		—		(19		)	11,603
Corporate	799		—		—			799
Total	$	100,661	$	63,805	$	(768	)	$	163,698



	Accounts		Unbilled		Less Allowance for			Accounts
March 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	44,356	$	19,381	$	(585	)	$	63,152
Gas Utilities	44,287		18,502		(936		)	61,853
Power Generation	265		—		—			265
Coal Mining	2,578		—		—			2,578
Oil and Gas	15,014		—		(105		)	14,909
Corporate	1,230		—		—			1,230
Total	$	107,730	$	37,883	$	(1,626	)	$	143,987

Notes Payable Notes Payable (Tables)

3 Months Ended

Mar. 31, 2013

Line of Credit Facility [Line Items]

Schedule of Notes Payable [Table Text Block]

We had the following short-term debt outstanding in the Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2013				Dec. 31, 2012				March 31, 2012
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	95,000	$	36,500	$	127,000	$	36,300	$	75,000	$	41,200
Term Loan due June 2013	150,000		—		150,000		—		150,000		—
Total	$	245,000	$	36,500	$	277,000	$	36,300	$	225,000	$	41,200

Credit Facility Covenants [Table Text Block]

Certain debt obligations require compliance with the following covenants at the end of each quarter (dollars in thousands):



	As of
	March 31, 2013			Covenant Requirement
Consolidated Net Worth	$	1,260,893		Greater than	$	946,493
Recourse Leverage Ratio	52.2		%	Less than	65.0		%

Earnings Per Share Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Schedule of Earnings Per Share Reconciliation [Table Text Block]

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



	Three Months Ended March 31,
	2013		2012

Income (loss) from continuing operations	$	43,197	$	35,271

Weighted average shares - basic	44,053		43,731
Dilutive effect of:
Restricted stock	155		147
Stock options	13		18
Other dilutive effects	91		73
Weighted average shares - diluted	44,312		43,969

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

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 March 31,
	2013	2012
Stock options	6	127
Restricted stock	34	31
Other stock	—	16
Anti-dilutive shares	40	174

Other Comprehensive Income Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2013

Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Comprehensive Income (Loss) [Table Text Block]

The components of the reclassification adjustments for the period, net of tax, included in Other Comprehensive Income were as follows (in thousands):



	Location on the Condensed Consolidated Statements of Income	Amount Reclassified from AOCI
	Location on the Condensed Consolidated Statements of Income	Three Months Ended March 31, 2013			Three Months Ended March 31, 2012
Gains and losses on cash flow hedges:
Interest rate swaps	Interest expense	$	1,796		$	1,822
Commodity contracts	Revenue	(1,092		)	(3,009		)
		704			(1,187		)
Income tax	Income tax benefit (expense)	(236		)	445
Total reclassification adjustments related to cash flow hedges, net of tax		$	468		$	(742	)

Amortization of defined benefit plans:
Prior service cost	Utilities - Operations and maintenance	$	(31	)	$	—
	Non-regulated energy operations and maintenance	(32		)	—

Actuarial gain (loss)	Utilities - Operations and maintenance	421			—
	Non-regulated energy operations and maintenance	274			—
		632			—
Income tax	Income tax benefit (expense)	(175		)	—
Total reclassification adjustments related to defined benefit plans, net of tax		$	457		$	—

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

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



	Derivatives Designated as Cash Flow Hedges			Employee Benefit Plans			Total
Balance as of December 31, 2011	$	(13,802	)	$	(19,076	)	$	(32,878	)
Other comprehensive income (loss), net of tax	(166		)	—			(166		)
Ending Balance March 31, 2012	$	(13,968	)	$	(19,076	)	$	(33,044	)

Balance as of December 31, 2012	$	(15,713	)	$	(19,775	)	$	(35,488	)
Other comprehensive income (loss), net of tax	(1,193		)	457			(736		)
Ending Balance March 31, 2013	$	(16,906	)	$	(19,318	)	$	(36,224	)

Employee Benefit Plans Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2013

Defined Benefit Plan Disclosure [Line Items]

Schedule of Defined Benefit Plans Contributions [Table Text Block]

Contributions and anticipated contributions are as follows (in thousands):



	Contributions Made		Additional
	Three Months Ended March 31, 2013		Contributions Anticipated for 2013		Contributions Anticipated for 2014
Defined Benefit Pension Plans	$	—	$	8,787	$	19,922
Non-pension Defined Benefit Postretirement Healthcare Plans	$	784	$	2,352	$	3,350
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	322	$	965	$	1,463

Defined Benefit Pension Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

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



	Three Months Ended March 31,
	2013			2012
Service cost	$	1,608		$	1,430
Interest cost	3,825			3,687
Expected return on plan assets	(4,654		)	(4,084		)
Prior service cost	16			22
Net loss (gain)	3,062			2,408
Net periodic benefit cost	$	3,857		$	3,463

Other Postretirement Benefit Plans, Defined Benefit [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

The components of net periodic benefit cost for the Non-pension Defined Benefit Postretirement Healthcare Plans were as follows (in thousands):



	Three Months Ended March 31,
	2013			2012
Service cost	$	419		$	402
Interest cost	417			523
Expected return on plan assets	(20		)	(19		)
Prior service cost (benefit)	(125		)	(125		)
Net loss (gain)	121			222
Net periodic benefit cost	$	812		$	1,003

Other Pension Plans, Postretirement or Supplemenatal Plans, Defined Benefit [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit and Defined Contribution Plans were as follows (in thousands):



	Three Months Ended March 31,
	2013		2012
Service cost	$	348	$	246
Interest cost	332		331
Prior service cost	1		1
Net loss (gain)	198		202
Net periodic benefit cost	$	879	$	780

Business Segment Information Business Segment Information (Tables)

3 Months Ended

Mar. 31, 2013

Segment Reporting Information, Additional Information [Abstract]

Schedule of Segment Reporting Information, by Segment [Table Text Block]

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



Three Months Ended March 31, 2013	External Operating Revenue		Intercompany Operating Revenue			Income (Loss) from Continuing Operations
Utilities:
Electric	$	158,483	$	4,147		$	12,356
Gas	199,812		—			18,483
Non-regulated Energy:
Power Generation	1,022		19,338			5,644
Coal Mining	6,010		7,573			1,065
Oil and Gas	15,344		—			(53		)
Corporate activities ^(a)	—		—			5,699
Intercompany eliminations	—		(31,058		)	3
Total	$	380,671	$	—		$	43,197



Three Months Ended March 31, 2012	External Operating Revenue		Intercompany Operating Revenue			Income (Loss) from Continuing Operations
Utilities:
Electric	$	156,133	$	3,036		$	8,746
Gas	180,522		—			15,207
Non-regulated Energy:
Power Generation	1,178		18,449			6,914
Coal Mining	6,373		8,616			1,000
Oil and Gas	21,645		—			13
Corporate activities ^(a)(b)	—		—			3,391
Intercompany eliminations	—		(30,101		)	—
Total	$	365,851	$	—		$	35,271

_____________


(a)	Income (loss) from continuing operations includes a $4.8 million and a $7.8 million net after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 and 2012, respectively.


(b)	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the three months ended March 31, 2012 were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.

Segment information and Corporate balances included in the accompanying Condensed Consolidated Balance Sheets was as follows (in thousands):



Total Assets (net of inter-company eliminations) as of:	March 31, 2013		Dec. 31, 2012		March 31, 2012
Utilities:
Electric ^(a)	$	2,367,014	$	2,387,458	$	2,268,524
Gas	752,468		765,165		717,185
Non-regulated Energy:
Power Generation^(a)	115,708		119,170		128,225
Coal Mining	82,839		83,810		87,139
Oil and Gas	255,786		258,460		430,851
Corporate activities	112,771		115,408		176,012
Total assets	$	3,686,586	$	3,729,471	$	3,807,936

___________


(a)	The PPA under which the Pueblo Airport Generation site owned by Colorado IPP supports Colorado customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total Assets of Electric Utilities Segment under this accounting for a capital lease.

- 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 Risk Management Activities (Tables)

3 Months Ended

Mar. 31, 2013

Derivative [Line Items]

Schedule of Derivative Instruments [Table Text Block]

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



	March 31, 2013						Dec. 31, 2012						March 31, 2012
	Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)			Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)			Designated Interest Rate Swaps^(a)			De-designated Interest Rate Swaps^(b)
Notional	$	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	3.75			0.75			4.00			1.00			4.75			1.75
Derivative liabilities, current	$	6,982		$	80,692		$	7,039		$	88,148		$	6,777		$	66,708
Derivative liabilities, non-current	$	15,237		$	—		$	16,941		$	—		$	18,441		$	17,237
Pre-tax accumulated other comprehensive income (loss)	$	(22,219	)	$	—		$	(23,980	)	$	—		$	(25,218	)	$	—
Pre-tax gain (loss)	$	—		$	7,456		$	—		$	1,882		$	—		$	12,045
Cash collateral receivable (payable) included in derivatives	$	—		$	5,960		$	—		$	5,960		$	—		$	—

_____________

(a)


(b)	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in 6 years and de-designated swaps totaling $150.0 million notional terminate in 16 years.

Schedule of Derivative Instruments Balance Sheet Location [Table Text Block]

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



As of March 31, 2013
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	832	$	—
Commodity derivatives	Derivative assets — non-current	206		—
Commodity derivatives	Derivative liabilities — current	—		3,110
Commodity derivatives	Derivative liabilities — non-current	—		1,114
Interest rate swaps	Derivative liabilities — current	—		6,982
Interest rate swaps	Derivative liabilities — non-current	—		15,237
Total derivatives designated as hedges		$	1,038	$	26,443

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,201	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		58
Commodity derivatives	Derivative liabilities — non-current	—		5,862
Interest rate swaps	Derivative liabilities — current	—		86,652
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	2,201	$	92,572



As of Dec. 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,874	$	—
Commodity derivatives	Derivative assets — non-current	510		—
Commodity derivatives	Derivative liabilities — current	—		1,993
Commodity derivatives	Derivative liabilities — non-current	—		821
Interest rate swaps	Derivative liabilities — current	—		7,038
Interest rate swaps	Derivative liabilities — non-current	—		16,941
Total derivatives designated as hedges		$	3,384	$	26,793

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	362	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	1,180		4,957
Commodity derivatives	Derivative liabilities — non-current	406		5,153
Interest rate swaps	Derivative liabilities — current	—		94,108
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	1,948	$	104,218



As of March 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	8,662	$	—
Commodity derivatives	Derivative assets — non-current	854		—
Commodity derivatives	Derivative liabilities — current	—		2,904
Commodity derivatives	Derivative liabilities — non-current	—		1,084
Interest rate swaps	Derivative liabilities — current	—		6,777
Interest rate swaps	Derivative liabilities — non-current	—		18,441
Total derivatives designated as hedges		$	9,516	$	29,206

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	—	$	8,436
Commodity derivatives	Derivative assets — non-current	—		(27		)
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		6,407
Interest rate swaps	Derivative liabilities — current	—		66,708
Interest rate swaps	Derivative liabilities — non-current	—		17,237
Total derivatives not designated as hedges		$	—	$	98,761

Oil and Gas [Member]

Derivative [Line Items]

Schedule of Derivative Instruments [Table Text Block]

We had the following derivatives and related balances for our Oil and Gas segment (dollars in thousands) as of:



	March 31, 2013					Dec. 31, 2012				March 31, 2012
	Crude oil futures, swaps and options		Natural gas futures and swaps			Crude oil futures, swaps and options		Natural gas futures and swaps		Crude oil futures, swaps and options			Natural gas futures and swaps
Notional ^(a)	522,000		10,633,000			528,000		8,215,500		522,000			5,001,750
Maximum terms in years ^(b)	0.75		0.5			1		0.75		1.25			1.5
Derivative assets, current	$	821	$	287		$	1,405	$	1,831	$	406		$	8,256
Derivative assets, non-current	$	—	$	—		$	297	$	170	$	46		$	808
Derivative liabilities, current	$	250	$	1,188		$	847	$	507	$	2,904		$	—
Derivative liabilities, non-current	$	—	$	—		$	—	$	—	$	1,084		$	—
Pre-tax accumulated other comprehensive income (loss)	$	10	$	(2,781	)	$	206	$	873	$	(3,566	)	$	9,064
Cash collateral receivable (payable) included in derivatives	$	730	$	1,880		$	786	$	620	$	—		$	—
Cash collateral included in Other current assets	$	723	$	2,102		$	1,078	$	709	$	—		$	—

____________


(a)	Crude oil in Bbls, natural gas in MMBtus.


(b)	Refers to the term of the derivative instrument. Assets and liabilities are classified as current/non-current based on the term of the hedged transaction and the corresponding settlement of the derivative instrument.

Utilities Group [Member]

Derivative [Line Items]

Contract or Notional Amounts and Terms of Commodity Derivatives[Table Text Block]

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



	March 31, 2013		Dec. 31, 2012		March 31, 2012
	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)
Natural gas futures purchased	13,180,000	80	15,350,000	83	11,550,000	81
Natural gas options purchased	440,000	5	2,430,000	2	670,000	12
Natural gas basis swaps purchased	11,350,000	69	12,020,000	72	7,640,000	81

Schedule of Derivative Instruments Balance Sheet Location [Table Text Block]

We had the following derivative balances related to the hedges in our Utilities (in thousands) as of:



	March 31, 2013		Dec. 31, 2012		March 31, 2012
Derivative assets, current	$	522	$	—	$	9,215
Derivative assets, non-current	$	—	$	43	$	27
Derivative liabilities, non-current	$	—	$	—	$	6,407
Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	4,315	$	9,596	$	15,223

Cash collateral receivable (payable) included in derivatives	$	4,487	$	8,576	$	17,651
Cash collateral included in Other current assets	$	3,295	$	4,354	$	—
Option premiums and commissions included in derivatives	$	350	$	1,063	$	407

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41641-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41638-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579240-113959

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

Reference 10: 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.(n)(2))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41620-113959

+ Details

Fair Value Measurements Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Derivative Instruments, Gain (Loss) [Line Items]

Schedule of Fair Value Hierarchy, Measured on Recurring Basis [Table Text Block]

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 March 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	71	$	—	$	(11	)	$	60
Basis Swaps -- Oil	—		836		—		(75		)	761
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		435		—		(148		)	287
Commodity derivatives — Utilities	—		1,897		—		(1,375		)	522
Cash equivalents ^(a)	12,397		—		—		—			12,397
Total	$	12,397	$	3,239	$	—	$	(1,609	)	$	14,027

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	396	$	—	$	(204	)	$	192
Basis Swaps -- Oil	—		670		—		(612		)	58
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		3,216		—		(2,028		)	1,188
Commodity derivatives — Utilities	—		5,862		—		(5,862		)	—
Interest rate swaps	—		108,871		—		(5,960		)	102,911
Total	$	—	$	119,015	$	—	$	(14,666	)	$	104,349

______________


(a)	Level 1 assets and liabilities are described in Note 13.



	As of Dec. 31, 2012
	Level 1		Level 2		Level 3			Cash Collateral and Counterparty Netting			Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	378	$	—		$	—		$	378
Basis Swaps -- Oil	—		1,325		—			—			1,325
Options -- Gas	—		—		—			—			—
Basis Swaps -- Gas	—		2,000		—			—			2,000
Commodity derivatives —Utilities	—		—		43		^(b)	—			43
Cash equivalents ^(a)	15,462		—		—			—			15,462
Total	$	15,462	$	3,703	$	43		$	—		$	19,208

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	1,131	$	—		$	(336	)	$	795
Basis Swaps -- Oil	—		502		—			(450		)	52
Options -- Gas	—		—		—			—			—
Basis Swaps -- Gas	—		1,127		—			(620		)	507
Commodity derivatives — Utilities	—		10,162		—			(10,162		)	—
Interest rate swaps	—		118,088		—			(5,960		)	112,128
Total	$	—	$	131,010	$	—		$	(17,528	)	$	113,482

______________


(a)	Level 1 assets and liabilities are described in Note 13.

(b)



	As of March 31, 2012
	Level 1		Level 2			Level 3			Cash Collateral and Counterparty Netting		Total
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	404		$	—		$	—	$	404
Basis Swaps -- Oil	—		48			—			—		48
Options -- Gas	—		—			—			—		—
Basis Swaps -- Gas	—		9,064			—			—		9,064
Commodity derivatives — Utilities	—		(8,412		)	3		^(b)	17,651		9,242
Cash equivalents ^(a)	55,919		—			—			—		55,919
Total	$	55,919	$	1,104		$	3		$	17,651	$	74,677

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	1,347		$	—		$	—	$	1,347
Basis Swaps -- Oil	—		2,641			—			—		2,641
Options -- Gas	—		—			—			—		—
Basis Swaps -- Gas	—		—			—			—		—
Commodity derivatives — Utilities	—		6,359			48		^(b)	—		6,407
Interest rate swaps	—		109,163			—			—		109,163
Total	$	—	$	119,510		$	48		$	—	$	119,558

______________


(a)	Level 1 assets and liabilities are described in Note 13.

(b)

Schedule of Derivative Instruments Balance Sheet Location [Table Text Block]

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



As of March 31, 2013
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	832	$	—
Commodity derivatives	Derivative assets — non-current	206		—
Commodity derivatives	Derivative liabilities — current	—		3,110
Commodity derivatives	Derivative liabilities — non-current	—		1,114
Interest rate swaps	Derivative liabilities — current	—		6,982
Interest rate swaps	Derivative liabilities — non-current	—		15,237
Total derivatives designated as hedges		$	1,038	$	26,443

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,201	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		58
Commodity derivatives	Derivative liabilities — non-current	—		5,862
Interest rate swaps	Derivative liabilities — current	—		86,652
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	2,201	$	92,572



As of Dec. 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	2,874	$	—
Commodity derivatives	Derivative assets — non-current	510		—
Commodity derivatives	Derivative liabilities — current	—		1,993
Commodity derivatives	Derivative liabilities — non-current	—		821
Interest rate swaps	Derivative liabilities — current	—		7,038
Interest rate swaps	Derivative liabilities — non-current	—		16,941
Total derivatives designated as hedges		$	3,384	$	26,793

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	362	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	1,180		4,957
Commodity derivatives	Derivative liabilities — non-current	406		5,153
Interest rate swaps	Derivative liabilities — current	—		94,108
Interest rate swaps	Derivative liabilities — non-current	—		—
Total derivatives not designated as hedges		$	1,948	$	104,218



As of March 31, 2012
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	8,662	$	—
Commodity derivatives	Derivative assets — non-current	854		—
Commodity derivatives	Derivative liabilities — current	—		2,904
Commodity derivatives	Derivative liabilities — non-current	—		1,084
Interest rate swaps	Derivative liabilities — current	—		6,777
Interest rate swaps	Derivative liabilities — non-current	—		18,441
Total derivatives designated as hedges		$	9,516	$	29,206

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	—	$	8,436
Commodity derivatives	Derivative assets — non-current	—		(27		)
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		6,407
Interest rate swaps	Derivative liabilities — current	—		66,708
Interest rate swaps	Derivative liabilities — non-current	—		17,237
Total derivatives not designated as hedges		$	—	$	98,761

Schedule of Derivative Offsetting On Balance Sheet [Table Text Block]

Offsetting of derivative assets and derivative liabilities as of March 31, 2013 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	75	$	—		$	(75	)	$	—
Oil and Gas - Crude Options	11		—			(11		)	—
Oil and Gas - Natural Gas Basis Swaps	148		—			(148		)	—
Utilities	1,897		(1,375		)	—			522
Total derivative assets subject to a master netting agreement or similar arrangement	2,131		(1,375		)	(234		)	522

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	761		—			—			761
Oil and Gas - Crude Options	60		—			—			60
Oil and Gas - Natural Gas Basis Swaps	287		—			—			287
Utilities	—		—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	1,108		—			—			1,108

Total derivative assets	$	3,239	$	(1,375	)	$	(234	)	$	1,630



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	612	$	—		$	(612	)	$	—
Oil and Gas - Crude Options	204		—			(204		)	—
Oil and Gas - Natural Gas Basis Swaps	2,028		—			(2,028		)	—
Utilities	5,862		(1,375		)	(4,487		)	—
Interest Rate Swaps	—		—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	8,706		(1,375		)	(7,331		)	—

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	58		—			—			58
Oil and Gas - Crude Options	192		—			—			192
Oil and Gas - Natural Gas Basis Swaps	1,188		—			—			1,188
Utilities	—		—			—			—
Interest Rate Swaps	108,871		—			(5,960		)	102,911
Total derivative liabilities not subject to a master netting agreement or similar arrangement	110,309		—			(5,960		)	104,349

Total derivative liabilities	$	119,015	$	(1,375	)	$	(13,291	)	$	104,349

Offsetting of derivative assets and derivative liabilities as of Dec. 31, 2012 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives		Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	76	$	—		$	—	$	76
Oil and Gas - Crude Options	93		—			—		93
Oil and Gas - Natural Gas Basis Swaps	172		—			—		172
Utilities	1,629		(1,586		)	—		43
Total derivative assets subject to a master netting agreement or similar arrangement	1,970		(1,586		)	—		384

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,249		—			—		1,249
Oil and Gas - Crude Options	285		—			—		285
Oil and Gas - Natural Gas Basis Swaps	1,828		—			—		1,828
Utilities	—		—			—		—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,362		—			—		3,362

Total derivative assets	$	5,332	$	(1,586	)	$	—	$	3,746



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets			Cash Collateral included in Derivatives			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	449	$	—		$	(449	)	$	—
Oil and Gas - Crude Options	337		—			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620		—			(620		)	—
Utilities	10,162		(1,586		)	(8,576		)	—
Interest Rate Swaps	—		—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568		(1,586		)	(9,982		)	—

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52		—			—			52
Oil and Gas - Crude Options	795		—			—			795
Oil and Gas - Natural Gas Basis Swaps	507		—			—			507
Utilities	—		—			—			—
Interest Rate Swaps	118,088		—			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442		—			(5,960		)	113,482

Total derivative liabilities	$	131,010	$	(1,586	)	$	(15,942	)	$	113,482

Offsetting of derivative assets and derivative liabilities as of March 31, 2012 (in thousands):



Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets		Cash Collateral included in Derivatives		Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—	$	—	$	—
Oil and Gas - Crude Options	—			—		—		—
Oil and Gas - Natural Gas Basis Swaps	—			—		—		—
Utilities	(8,409		)	—		17,651		9,242
Total derivative assets subject to a master netting agreement or similar arrangement	(8,409		)	—		17,651		9,242

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	48			—		—		48
Oil and Gas - Crude Options	404			—		—		404
Oil and Gas - Natural Gas Basis Swaps	9,064			—		—		9,064
Utilities	—			—		—		—
Total derivative assets not subject to a master netting agreement or similar arrangement	9,516			—		—		9,516

Total derivative assets	$	1,107		$	—	$	17,651	$	18,758



Derivative Liabilities	Gross Amounts of Derivative Liabilities		Gross Amounts Offset on Condensed Consolidated Balance Sheets		Cash Collateral included in Derivatives		Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—	$	—	$	—	$	—
Oil and Gas - Crude Options	—		—		—		—
Oil and Gas - Natural Gas Basis Swaps	—		—		—		—
Utilities	6,407		—		—		6,407
Interest Rate Swaps	—		—		—		—
Total derivative liabilities subject to a master netting agreement or similar arrangement	6,407		—		—		6,407

Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	2,641		—		—		2,641
Oil and Gas - Crude Options	1,347		—		—		1,347
Oil and Gas - Natural Gas Basis Swaps	—		—		—		—
Utilities	—		—		—		—
Interest Rate Swaps	109,163		—		—		109,163
Total derivative liabilities not subject to a master netting agreement or similar arrangement	113,151		—		—		113,151

Total derivative liabilities	$	119,558	$	—	$	—	$	119,558

Schedule of Collateral Held by Counterparties [Table Text Block]

Derivative assets and derivative liabilities and collateral held by counterparty as of March 31, 2013 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	1,108		—		1,108
Utilities	Counterparty A	522		—		522
		$	1,630	$	—	$	1,630



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—	$	(2,825	)	$	(2,825	)
Oil and Gas	Counterparty B	1,438		—			1,438
Utilities	Counterparty A	—		(3,295		)	(3,295		)
Interest Rate Swap	Counterparty D	4,266		—			4,266
Interest Rate Swap	Counterparty E	26,754		—			26,754
Interest Rate Swap	Counterparty F	11,841		—			11,841
Interest Rate Swap	Counterparty G	24,905		—			24,905
Interest Rate Swap	Counterparty H	14,625		—			14,625
Interest Rate Swap	Counterparty I	20,520		—			20,520
		$	104,349	$	(6,120	)	$	98,229

Derivative assets and derivative liabilities and collateral held by counterparty as of Dec. 31, 2012 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	341	$	—	$	341
Oil and Gas	Counterparty B	3,362		—		3,362
Utilities	Counterparty A	43		—		43
		$	3,746	$	—	$	3,746



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—	$	(1,787	)	$	(1,787	)
Oil and Gas	Counterparty B	1,354		—			1,354
Utilities	Counterparty A	—		(4,354		)	(4,354		)
Interest Rate Swap	Counterparty D	4,588		—			4,588
Interest Rate Swap	Counterparty E	29,245		—			29,245
Interest Rate Swap	Counterparty F	12,721		—			12,721
Interest Rate Swap	Counterparty G	26,520		—			26,520
Interest Rate Swap	Counterparty H	16,809		—			16,809
Interest Rate Swap	Counterparty I	22,245		—			22,245
		$	113,482	$	(6,141	)	$	107,341

Derivative assets and derivative liabilities and collateral held by counterparty as of March 31, 2012 (in thousands):



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets		Cash Collateral Received		Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	9,516		—		9,516
Utilities	Counterparty A	9,242		—		9,242
		$	18,758	$	—	$	18,758



				Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities		Cash Collateral Paid		Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—	$	—	$	—
Oil and Gas	Counterparty B	3,988		—		3,988
Utilities	Counterparty A	6,407		—		6,407
Interest Rate Swap	Counterparty D	4,810		—		4,810
Interest Rate Swap	Counterparty E	27,137		—		27,137
Interest Rate Swap	Counterparty F	13,027		—		13,027
Interest Rate Swap	Counterparty G	24,617		—		24,617
Interest Rate Swap	Counterparty H	19,808		—		19,808
Interest Rate Swap	Counterparty I	19,764		—		19,764
		$	119,558	$	—	$	119,558

Cash Flow Hedging [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Schedule of Cash Flow Hedges, Gain (Loss) in Statements of Income and Balance Sheet, Location

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



Three Months Ended March 31, 2013
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	$	(19	)	Interest expense	$	(1,796	)		$	—
Commodity derivatives	(2,759		)	Revenue	1,092				—
Total	$	(2,778	)		$	(704	)		$	—



Three Months Ended March 31, 2012
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	$	(762	)	Interest expense	$	(1,822	)		$	—
Commodity derivatives	1,283			Revenue	3,009				—
Total	$	521			$	1,187			$	—

Not Designated as Hedging Instrument [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Income and Balance Sheets, Location [Table Text Block]

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



		Three Months Ended
		March 31, 2013
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income
Interest rate swaps - unrealized	Unrealized gain (loss) on interest rate swaps, net	$	7,456
Interest rate swaps - realized	Interest expense	(3,427		)
		$	4,029



		Three Months Ended
		March 31, 2012
Derivatives Not Designated as Hedging Instruments	Location of Gain/(Loss) on Derivatives Recognized in Income	Amount of Gain/(Loss) on Derivatives Recognized in Income
Interest rate swaps - unrealized	Unrealized gain (loss) on interest rate swaps, net	$	12,045
Interest rate swaps - realized	Interest expense	(3,205		)
		$	8,840

- 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 Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value of Financial Instruments [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

The estimated fair values of our financial instruments are as follows (in thousands) as of:



	March 31, 2013				Dec. 31, 2012				March 31, 2012
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents ^(a)	$	12,397	$	12,397	$	15,462	$	15,462	$	56,132	$	56,132
Restricted cash and equivalents ^(a)	$	6,846	$	6,846	$	7,916	$	7,916	$	8,960	$	8,960
Notes payable ^(a)	$	245,000	$	245,000	$	277,000	$	277,000	$	225,000	$	225,000
Long-term debt, including current maturities ^(b)	$	1,041,114	$	1,208,909	$	1,042,850	$	1,231,559	$	1,280,993	$	1,439,724

____________


(a)	Fair value approximates carrying value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates and therefore is classified in Level 1 in the fair value hierarchy.


(b)	Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

- 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 Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13476-108611

Reference 2: 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=7578670&loc=d3e19207-110258

Reference 3: 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=7491637&loc=d3e13467-108611

Reference 4: 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

Reference 5: 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 6: 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=7491637&loc=d3e13433-108611

Reference 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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.

+ Details

Supplemental Cash Flow Information Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Non-cash Investing and Financing Activities from Continuing Operations [Abstract]
Property, plant and equipment acquired wtih accrued liabilities	$ 31,780	$ 31,644
Increase (decrease) in capitalized assets associated with asset retirement obligations	0	2,826
Cash (paid) refunded during the period for continuing operations [Abstract]
Interest (net of amounts capitalized)	12,768	16,799
Income taxes, net	$ 4,656	$ 1,838

Materials, Supplies and Fuel Materials, Supplies and Fuel (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Materials and Supplies	$ 50,401	$ 43,397	$ 44,361
Total materials, supplies and fuel	64,189	77,643	63,236
Electric Utilities [Member]
Fuel - Electric Utilities	8,445	8,589	7,812
Gas Utilities [Member]
Natural gas in storage held for distribution	$ 5,343	$ 25,657	$ 11,063

Accounts Receivable and Allowance for Doubtful Accounts Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	$ (1,393)	$ (768)	$ (1,626)
Accounts receivable, net	168,783	163,698	143,987
Corporate [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	1,026	799	1,230
Electric Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(623)	(527)	(585)
Accounts receivable, net	68,864	77,798	63,152
Gas Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(751)	(222)	(936)
Accounts receivable, net	86,712	71,235	61,853
Power Generation [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	3	16	265
Coal Mining [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	1,857	2,247	2,578
Oil and Gas [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(19)	(19)	(105)
Accounts receivable, net	10,321	11,603	14,909
Billed Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	120,146	100,661	107,730
Billed Revenues [Member] \| Corporate [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	1,026	799	1,230
Billed Revenues [Member] \| Electric Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	47,896	54,482	44,356
Billed Revenues [Member] \| Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	59,024	31,495	44,287
Billed Revenues [Member] \| Power Generation [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	3	16	265
Billed Revenues [Member] \| Coal Mining [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	1,857	2,247	2,578
Billed Revenues [Member] \| Oil and Gas [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	10,340	11,622	15,014
Unbilled Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	50,030	63,805	37,883
Unbilled Revenues [Member] \| Corporate [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] \| Electric Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	21,591	23,843	19,381
Unbilled Revenues [Member] \| Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	28,439	39,962	18,502
Unbilled Revenues [Member] \| Power Generation [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] \| Coal Mining [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] \| Oil and Gas [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	$ 0	$ 0	$ 0

Notes Payable Notes Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Line of Credit Facility [Line Items]
Notes payable	$ 245,000	$ 277,000	$ 225,000
Letters of Credit Outstanding, Amount	36,500	36,300	41,200
Debt Disclosure [Abstract]
Consolidated Net Worth	1,260,893	1,232,509	1,224,692
Line of Credit [Member]
Debt Disclosure [Abstract]
Consolidated Net Worth, Minimum Requirement	$ 946,493
Recourse Leverage Ratio	52.20%
Recourse Leverage Ratio, Maximum Allowed, Covenant	65.00%
Line of Credit [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Notes payable	$ 95,000	127,000	75,000
Letters of Credit Outstanding, Amount	36,500	36,300	41,200
Loans Payable [Member] \| Corporate Term Loan due June 2013 [Member]
Line of Credit Facility [Line Items]
Notes payable	150,000	150,000	150,000
Letters of Credit Outstanding, Amount	$ 0	$ 0	$ 0

Earnings Per Share Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Debt Instrument [Line Items]
Income (loss) from continuing operations	$ 43,197	$ 35,271
Weighted Average Shares, Basic	44,053	43,731
Dilutive Effect on Basic Earnings Per Share [Abstract]
Restricted Stock and Restricted Stock Units, Shares	155	147
Stock Options, Shares	13	18
Other Dilutive Effects, Shares	91	73
Weighted Average Shares, Diluted	44,312	43,969

- 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 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 2: 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=7655603&loc=d3e1448-109256

Reference 3: 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 4: 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.

Reference 5: 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 6: 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 7: 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.

+ Details

Earnings Per Share Anti-dilutive shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	40	174
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	6	127
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	34	31
Other Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	16

- 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 Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: 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 3: 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 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 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 6: 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 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.

Reference 8: 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.

+ Details

Other Comprehensive Income Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Costs Incurred	$ 23,672	$ 29,914
Revenue	380,671	365,851
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	64,860	55,044
Income Tax Expense (Benefit)	21,577	19,717
Net income (loss) available for common stock	43,197	29,787
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	704	(1,187)
Income Tax Expense (Benefit)	236	(445)
Net income (loss) available for common stock	468	(742)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash Flow Hedging [Member] \| Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Costs Incurred	1,796	1,822
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Cash Flow Hedging [Member] \| Commodity Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenue	(1,092)	(3,009)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	632	0
Income Tax Expense (Benefit)	175	0
Net income (loss) available for common stock	457	0
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Defined Benefit Plans Adjustment [Member] \| Utilities - Operations and maintenance [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	(31)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	421	0
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Defined Benefit Plans Adjustment [Member] \| Non-regulated energy operations and maintenance [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	(32)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	$ 274	$ 0

Other Comprehensive Income Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	$ (35,488)	$ (32,878)
Other Comprehensive Income (Loss), Net of Tax	(736)	(166)
Accumulated other comprehensive income (loss), Ending Balance	(36,224)	(33,044)
Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	(15,713)	(13,802)
Other Comprehensive Income (Loss), Net of Tax	(1,193)	(166)
Accumulated other comprehensive income (loss), Ending Balance	(16,906)	(13,968)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	(19,775)	(19,076)
Other Comprehensive Income (Loss), Net of Tax	457	0
Accumulated other comprehensive income (loss), Ending Balance	$ (19,318)	$ (19,076)

- 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

Reference 1: 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=20435746&loc=d3e637-108580

Reference 2: 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=20435746&loc=d3e681-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669686-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 31
-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 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 6: 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 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 14, 17, 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 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Employee Benefit Plans Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service Cost	$ 1,608	$ 1,430
Interest Cost	3,825	3,687
Expected Return on Plan Assets	(4,654)	(4,084)
Prior Service Cost (Benefit)	16	22
Net Loss (Gain)	3,062	2,408
Net Periodic Benefit Cost	3,857	3,463
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions Made by Employer	0
Additional Employer Contributions Anticipated in Current Fiscal Year	8,787
Estimated Future Employer Contributions in Next Fiscal Year	19,922
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service Cost	419	402
Interest Cost	417	523
Expected Return on Plan Assets	(20)	(19)
Prior Service Cost (Benefit)	(125)	(125)
Net Loss (Gain)	121	222
Net Periodic Benefit Cost	812	1,003
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions Made by Employer	784
Additional Employer Contributions Anticipated in Current Fiscal Year	2,352
Estimated Future Employer Contributions in Next Fiscal Year	3,350
Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service Cost	348	246
Interest Cost	332	331
Prior Service Cost (Benefit)	1	1
Net Loss (Gain)	198	202
Net Periodic Benefit Cost	879	$ 780
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions Made by Employer	322
Additional Employer Contributions Anticipated in Current Fiscal Year	965
Estimated Future Employer Contributions in Next Fiscal Year	$ 1,463

Business Segment Information Information Relating to Segment Statement of Income (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Segment Reporting Information [Line Items]

External Operating Revenue

$ 380,671

$ 365,851

Intersegment Operating Revenue

Income (Loss) from Continuing Operations

43,197

35,271

Mark-to-market gain (loss) on certain interest rate swaps, net of tax

(4,800)

(7,800)

Overhead Of Discontinued Operations, Net of Tax

1,600

Corporate [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

Intersegment Operating Revenue

Income (Loss) from Continuing Operations

^[1]

5,699

3,391

^[2]

Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

Intersegment Operating Revenue

(31,058)

(30,101)

Income (Loss) from Continuing Operations

Electric Utilities [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

158,483

156,133

Intersegment Operating Revenue

4,147

3,036

Income (Loss) from Continuing Operations

12,356

8,746

Gas Utilities [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

199,812

180,522

Intersegment Operating Revenue

Income (Loss) from Continuing Operations

18,483

15,207

Power Generation [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

1,022

1,178

Intersegment Operating Revenue

19,338

18,449

Income (Loss) from Continuing Operations

5,644

6,914

Coal Mining [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

6,010

6,373

Intersegment Operating Revenue

7,573

8,616

Income (Loss) from Continuing Operations

1,065

1,000

Oil and Gas [Member]

Segment Reporting Information [Line Items]

External Operating Revenue

15,344

21,645

Intersegment Operating Revenue

Income (Loss) from Continuing Operations

$ (53)

$ 13

[1]	Income (loss) from continuing operations includes a $4.8 million and a $7.8 million net after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 and 2012, respectively.
[2]	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the three months ended March 31, 2012 were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.

Business Segment Information Segment Assets (Details) - USD ($)
$ in Thousands

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2012

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

$ 3,686,586

$ 3,729,471

$ 3,807,936

Corporate [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

112,771

115,408

176,012

Electric Utilities [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

^[1]

2,367,014

2,387,458

2,268,524

Gas Utilities [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

752,468

765,165

717,185

Power Generation [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

^[1]

115,708

119,170

128,225

Coal Mining [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

82,839

83,810

87,139

Oil and Gas [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

$ 255,786

$ 258,460

$ 430,851

[1]	The PPA under which the Pueblo Airport Generation site owned by Colorado IPP supports Colorado customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total Assets of Electric Utilities Segment under this accounting for a capital lease.

Risk Management Activities Risk Management Activities (Details)
$ in Thousands

3 Months Ended

12 Months Ended

Mar. 31, 2013

USD ($)

bbl

MMBTU

Mar. 31, 2012

USD ($)

bbl

MMBTU

Dec. 31, 2012

USD ($)

bbl

MMBTU

Derivative [Line Items]

Credit Exposure, Non-Investment Grade Company

$ 2,300

Derivative assets, current

1,630

$ 17,877

$ 3,236

Derivative assets, non-current

881

510

Derivative liabilities, current

89,112

76,389

96,541

Derivative liabilities, non-current

15,237

43,169

16,941

Cash Collateral included in other current assets

6,120

6,141

Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Derivative liabilities, current

6,982

6,777

7,039

Derivative liabilities, non-current

15,237

18,441

16,941

Accumulated Other Comprehensive Income Loss Pre Tax

(22,219)

(25,218)

(23,980)

Cash collateral receivable (payable) included in Derivatives

$ 0

Derivative, Remaining Maturity

3 years 9 months

4 years 9 months

4 years

Notional Amount, Interest Rate Derivatives

^[1]

$ 150,000

Weighted Average Fixed Interest Rate

5.04%

Pre-tax gain (loss) included in Consolidated Statement of Income

$ 0

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

(7,000)

Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Derivative liabilities, current

80,692

66,708

88,148

Derivative liabilities, non-current

17,237

Accumulated Other Comprehensive Income Loss Pre Tax

Cash collateral receivable (payable) included in Derivatives

$ 5,960

$ 0

$ 5,960

Derivative, Remaining Maturity

9 months

1 year 9 months

1 year

Notional Amount, Interest Rate Derivatives

^[2]

$ 250,000

Weighted Average Fixed Interest Rate

5.67%

Pre-tax gain (loss) included in Consolidated Statement of Income

$ 7,456

$ 12,045

$ 1,882

Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Dedesignated Interest Rate Swap Expiring 2018 [Member]

Derivative [Line Items]

Derivative, Remaining Maturity

6 years

Notional Amount, Interest Rate Derivatives

$ 100,000

Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Dedesignated Interest Rate Swaps Expiring 2028 [Member]

Derivative [Line Items]

Derivative, Remaining Maturity

16 years

Notional Amount, Interest Rate Derivatives

$ 150,000

Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Credit Risk [Member]

Derivative [Line Items]

Notional Amount, Interest Rate Derivatives

50,000

Potential Future Exposure on Credit Related Contingent Feature

20,000

Black Hills Corporation [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Notional Amount, Interest Rate Derivatives

75,000

Utilities Group [Member] | Natural Gas, Distribution [Member]

Derivative [Line Items]

Derivative assets, current

522

9,215

Derivative assets, non-current

Derivative liabilities, non-current

6,407

Cash collateral receivable (payable) included in Derivatives

4,487

17,651

8,576

Cash Collateral included in other current assets

3,295

4,354

Net Unrealized Gain (Loss) Included in Regulatory Assets or Regulatory liabilities

4,315

15,223

9,596

Option Premium and commission included in Derivatives

$ 350

$ 407

$ 1,063

Utilities Group [Member] | Future [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

13,180,000

11,550,000

15,350,000

Derivative, Remaining Maturity

80 months

81 months

83 months

Utilities Group [Member] | Commodity Option [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

440,000

670,000

2,430,000

Derivative, Remaining Maturity

5 months

12 months

2 months

Utilities Group [Member] | Basis Swap [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

11,350,000

7,640,000

12,020,000

Derivative, Remaining Maturity

69 months

81 months

72 months

Oil and Gas [Member]

Derivative [Line Items]

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

$ (200)

Oil and Gas [Member] | Crude Oil [Member]

Derivative [Line Items]

Cash collateral receivable (payable) included in Derivatives

730

$ 0

$ 786

Cash Collateral included in other current assets

723

1,078

Oil and Gas [Member] | Natural Gas [Member]

Derivative [Line Items]

Cash collateral receivable (payable) included in Derivatives

1,880

620

Cash Collateral included in other current assets

$ 2,102

$ 0

$ 709

Oil and Gas [Member] | Swaps, Options and Futures [Member] | Crude Oil [Member]

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | bbl

^[3]

522,000

528,000

Maximum Length of Time Hedged in Cash Flow Hedge

^[4]

9 months

1 year 3 months

1 year

Derivative assets, current

$ 821

$ 406

$ 1,405

Derivative assets, non-current

297

Derivative liabilities, current

250

2,904

847

Derivative liabilities, non-current

1,084

Accumulated Other Comprehensive Income Loss Pre Tax

$ 10

$ (3,566)

$ 206

Oil and Gas [Member] | Swaps and Futures [Member] | Natural Gas [Member]

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

^[3]

10,633,000

5,001,750

8,215,500

Maximum Length of Time Hedged in Cash Flow Hedge

^[4]

6 months

1 year 6 months

9 months

Derivative assets, current

$ 287

$ 8,256

$ 1,831

Derivative assets, non-current

808

170

Derivative liabilities, current

1,188

507

Derivative liabilities, non-current

Accumulated Other Comprehensive Income Loss Pre Tax

(2,781)

$ 9,064

$ 873

Power Generation [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Notional Amount, Interest Rate Derivatives

$ 75,000

[1]	These swaps have been designated to $75.0 million of borrowings on our Revolving Credit Facility and $75.0 million of borrowings on our project financing debt at Black Hills Wyoming. The swaps transferred to Black Hills Wyoming such that BHC and Black Hills Wyoming are both jointly and severally liable for the amount of those obligations. These swaps are priced using three-month LIBOR, matching the floating portion of the related swaps.
[2]	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in 6 years and de-designated swaps totaling $150.0 million notional terminate in 16 years.
[3]	Crude oil in Bbls, natural gas in MMBtus.
[4]	Refers to the term of the derivative instrument. Assets and liabilities are classified as current/non-current based on the term of the hedged transaction and the corresponding settlement of the derivative instrument.

Fair Value Measurements Fair Value Hierarchy (Details) - USD ($)
$ in Thousands

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2012

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

$ 1,630

$ 3,746

$ 18,758

Fair Value, Transfers Between Level 1 and Level 2, Description and Policy [Abstract]

Fair Value, Assets, Level 1 to Level 2 Transfers, Amount

Fair Value, Assets, Level 2 to Level 1 Transfers, Amount

Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount

Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash and Cash Equivalents, Fair Value Disclosure

^[1]

12,397

15,462

55,919

Assets, Fair Value Disclosure

12,397

15,462

55,919

Liabilities, Fair Value Disclosure

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash and Cash Equivalents, Fair Value Disclosure

Assets, Fair Value Disclosure

3,239

3,703

1,104

Liabilities, Fair Value Disclosure

119,015

131,010

119,510

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash and Cash Equivalents, Fair Value Disclosure

Assets, Fair Value Disclosure

Liabilities, Fair Value Disclosure

Fair Value, Measurements, Recurring [Member] | Netting [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash and Cash Equivalents, Fair Value Disclosure

Assets, Fair Value Disclosure

(1,609)

17,651

Liabilities, Fair Value Disclosure

(14,666)

(17,528)

Fair Value, Measurements, Recurring [Member] | Fair Value [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash and Cash Equivalents, Fair Value Disclosure

12,397

15,462

55,919

Assets, Fair Value Disclosure

14,027

19,208

74,677

Liabilities, Fair Value Disclosure

104,349

113,482

119,558

Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

108,871

118,088

109,163

Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

(5,960)

Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

102,911

112,128

109,163

Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

378

404

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

396

1,131

1,347

Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

(11)

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

(204)

(336)

Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

378

404

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

192

795

1,347

Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

836

1,325

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

670

502

2,641

Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

(75)

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

(612)

(450)

Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

761

1,325

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

2,641

Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

435

2,000

9,064

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

3,216

1,127

Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

(148)

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

(2,028)

(620)

Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Oil and Gas [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

287

2,000

9,064

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

1,188

507

Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Utilities Group [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Utilities Group [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

1,897

(8,412)

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

5,862

10,162

6,359

Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Utilities Group [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

^[2]

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

^[2]

Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Utilities Group [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

(1,375)

17,651

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

(5,862)

(10,162)

Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Utilities Group [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Derivative Assets

522

9,242

Derivative Financial Instruments, Liabilities, Fair Value Disclosure

$ 0

$ 6,407

[1]

Level 1 assets and liabilities are described in Note 13.

[2]

Fair Value Measurements Fair Value Measurements Balance Sheet Location (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	$ 1,038	$ 3,384	$ 9,516
Derivative Liability, Fair Value, Net	26,443	26,793	29,206
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	2,201	1,948	0
Derivative Liability, Fair Value, Net	92,572	104,218	98,761
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Assets, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	832	2,874	8,662
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Assets, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	206	510	854
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	3,110	1,993	2,904
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	1,114	821	1,084
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Assets, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,201	362	0
Derivative Asset, Fair Value, Gross Liability	0	0	8,436
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Assets, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0	0
Derivative Asset, Fair Value, Gross Liability	0	0	(27)
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	1,180	0
Derivative Liability, Fair Value, Gross Liability	58	4,957	0
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	406	0
Derivative Liability, Fair Value, Gross Liability	5,862	5,153	6,407
Interest Rate Swap [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	6,982	7,038	6,777
Interest Rate Swap [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	15,237	16,941	18,441
Interest Rate Swap [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	86,652	94,108	66,708
Interest Rate Swap [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0	$ 17,237

Fair Value Measurements Fair Value Balance Sheet Offsetting by Counterparty (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	$ 1,630	$ 3,746	$ 18,758
Derivative, Collateral, Obligation to Return Cash	0	0	0
Net Amount with Counterparty, after cash collateral and netting	1,630	3,746	18,758
Derivative Liabilities	104,349	113,482	119,558
Derivative, Collateral, Right to Reclaim Cash	(6,120)	(6,141)	0
Net Amount with Counterparty, after collateral and netting	98,229	107,341	119,558
Counterparty D [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	4,266	4,588	4,810
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	4,266	4,588	4,810
Counterparty E [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	26,754	29,245	27,137
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	26,754	29,245	27,137
Counterparty F [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	11,841	12,721	13,027
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	11,841	12,721	13,027
Counterparty G [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	24,905	26,520	24,617
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	24,905	26,520	24,617
Counterparty H [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	14,625	16,809	19,808
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	14,625	16,809	19,808
Counteryparty I [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liabilities	20,520	22,245	19,764
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	20,520	22,245	19,764
Utilities Group [Member] \| Counterparty A [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	522	43	9,242
Derivative, Collateral, Obligation to Return Cash	0	0	0
Net Amount with Counterparty, after cash collateral and netting	522	43	9,242
Derivative Liabilities	0	0	6,407
Derivative, Collateral, Right to Reclaim Cash	(3,295)	(4,354)	0
Net Amount with Counterparty, after collateral and netting	(3,295)	(4,354)	6,407
Oil and Gas [Member] \| Counterparty A [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	0	341	0
Derivative, Collateral, Obligation to Return Cash	0	0	0
Net Amount with Counterparty, after cash collateral and netting	0	341	0
Derivative Liabilities	0	0	0
Derivative, Collateral, Right to Reclaim Cash	(2,825)	(1,787)	0
Net Amount with Counterparty, after collateral and netting	(2,825)	(1,787)	0
Oil and Gas [Member] \| Counterparty B [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	1,108	3,362	9,516
Derivative, Collateral, Obligation to Return Cash	0	0	0
Net Amount with Counterparty, after cash collateral and netting	1,108	3,362	9,516
Derivative Liabilities	1,438	1,354	3,988
Derivative, Collateral, Right to Reclaim Cash	0	0	0
Net Amount with Counterparty, after collateral and netting	$ 1,438	$ 1,354	$ 3,988

Fair Value Measurements Fair Value Measurements Hedging Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 4,029	$ 8,840
Cash Flow Hedging [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(2,778)	521
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(704)	1,187
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Cash Flow Hedging [Member] \| Interest Rate Swap [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(19)	(762)
Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Interest Expense [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1,796)	(1,822)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(2,759)	1,283
Cash Flow Hedging [Member] \| Commodity Contract [Member] \| Sales Revenue, Goods, Net [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1,092	3,009
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member] \| Unrealized Gain Loss on Interest Rate Swaps [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	7,456	12,045
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member] \| Interest Expense [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (3,427)	$ (3,205)

Fair Value of Financial Instruments Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2012

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Cash and Cash Equivalents, at Carrying Value

$ 12,397

$ 15,462

$ 56,132

Restricted Cash and Investments, at Carrying Value

6,846

7,916

8,960

Notes Payable, at Carrying Value

245,000

277,000

225,000

Carrying Amount [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Cash and Cash Equivalents, at Carrying Value

12,397

15,462

56,132

Restricted Cash and Investments, at Carrying Value

6,846

7,916

8,960

Notes Payable, at Carrying Value

245,000

277,000

225,000

Long-term Debt, at Carrying Value

1,041,114

1,042,850

1,280,993

Fair Value [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Cash and Cash Equivalents, at Fair Value

^[1]

12,397

15,462

56,132

Restricted Cash and Equivalents, at Fair Value

^[1]

6,846

7,916

8,960

Notes Payable, at Fair Value

^[1]

245,000

277,000

225,000

Long-term Debt, at Fair Value

^[2]

$ 1,208,909

$ 1,231,559

$ 1,439,724

[1]	Fair value approximates carrying value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates and therefore is classified in Level 1 in the fair value hierarchy.
[2]	Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2013 USD ($) MW
Loss from Catastrophes [Member]
Long-term Purchase Commitment [Line Items]
Loss Contingency, Damages Sought, Value	$ 8.0
Cheyenne Prairie [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 222.0
Cheyenne Prairie [Member] \| Equipment [Member]
Long-term Purchase Commitment [Line Items]
Long Term Purchase Commitment, Percentage Committed	28.00%
Cheyenne Prairie [Member] \| Construction Contracts [Member]
Long-term Purchase Commitment [Line Items]
Long Term Purchase Commitment, Percentage Committed	13.00%
Basin Electric [Member]
Long-term Purchase Commitment [Line Items]
Number of Megawatts Capacity Purchased Under Long-term Contract \| MW	40
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	Sep. 30, 2014

Commitments and Contingencies Supply Agreements (Details) - Basin Electric [Member]	3 Months Ended
	Mar. 31, 2013 MW
Supply Commitment [Line Items]
Number of Megawatts Sold Under Long-Term Contract	40
Long-term Contract To Sell Electric Power, Date of Contract Expiration	Sep. 30, 2014

Commitments and Contingencies Dividend Restrictions (Details) $ in Millions	Mar. 31, 2013 USD ($)
Utilities Group [Member]
Related Party Transaction [Line Items]
Restricted Net Assets for Subsidiaries	$ 205.9
Non Regulated Energy Group [Member]
Related Party Transaction [Line Items]
Restricted Net Assets for Subsidiaries	$ 100.0

Commitments and Contingencies Guarantees (Details) - Electric Utilities [Member] - Wind Turbines [Member] $ in Millions	Mar. 29, 2013 USD ($)
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 33.3
Guarantee Expiration Date	Mar. 29, 2013

Label

Element

Value

Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents

us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents

$ 37,100,000

^[1]

[1]	Includes cash of discontinued operations of $37.1 million at Dec. 31, 2011.

- Definition

For the disposal group, including a component of the entity (discontinued operation), cash includes currency on hand as well as demand deposits with banks or financial institutions. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References + Details