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Document and Entity Information Document - shares	3 Months Ended
Document and Entity Information Document - shares	Mar. 31, 2014	Apr. 29, 2014
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, 2014
Amendment Flag	false
Document Fiscal Year Focus	2014
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		44,628,586
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No

Condensed Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Revenue	$ 460,169	$ 380,671
Utilities -
Fuel, purchased power and cost of gas sold	230,468	168,173
Operations and maintenance	71,227	65,690
Non-regulated energy operations and maintenance	22,332	21,329
Depreciation, depletion and amortization	36,083	34,781
Taxes - property, production and severance	10,336	10,380
Other operating expenses	125	472
Total operating expenses	370,571	300,825
Operating income	89,598	79,846
Interest charges -
Interest expense incurred (including amortization of debt issuance costs, premiums and discounts and realized settlements on interest rate swaps)	(17,860)	(23,672)
Allowance for funds used during construction - borrowed	270	74
Capitalized interest	257	266
Unrealized gain (loss) on interest rate swaps, net	0	7,456
Interest income	390	285
Allowance for funds used during construction - equity	238	200
Other income (expense), net	592	405
Total other income (expense), net	(16,113)	(14,986)
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	73,485	64,860
Equity in earnings (loss) of unconsolidated subsidiaries	(1)	(86)
Income tax benefit (expense)	(25,366)	(21,577)
Net income (loss) available for common stock	$ 48,118	$ 43,197
Earnings (loss) per share, Basic -
Total income (loss) per share, Basic	$ 1.09	$ 0.98
Earnings (loss) per share, Diluted -
Total income (loss) per share, Diluted	$ 1.08	$ 0.97
Weighted Average Number of Shares Outstanding:
Basic	44,330	44,053
Diluted	44,554	44,312
Dividends paid per share of common stock	$ 0.39	$ 0.38

Condensed Consolidated Statement of Comprehensive Income (unaudited) Statement - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net income (loss) available for common stock	$ 48,118	$ 43,197
Other comprehensive income (loss), net of tax:
Fair value adjustments on derivatives designated as cash flow hedges (net of tax (expense) benefit of $1,307 and $1,117, respectively)	(2,257)	(1,661)
Reclassification adjustments for cash flow hedges settled and included in net income (loss) (net of tax (expense) benefit of $(425) and $(236), respectively)	780	468
Benefit plan liability adjustments - net gain (loss) (net of tax of $2 and $0, respectively)	(2)	0
Benefit plan liability adjustments - prior service (costs) (net of tax of $(90) and $0, respectively)	164	0
Reclassification adjustments of benefit plan liability - prior service cost (net of tax of $4 and $17, respectively)	(9)	(46)
Reclassification adjustments of benefit plan liability - net gain (loss) (net of tax of $(85) and $(192), respectively)	157	503
Other comprehensive income (loss), net of tax	(1,167)	(736)
Comprehensive income (loss) available for common stock	46,951	42,461
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Parenthetical Disclosures
Fair value adjustment on derivatives designated as cash flow hedges, (tax) benefit	1,307	1,117
Reclassification adjustments of cash flow hedges settled and included in net income, (tax) benefit	(425)	(236)
Benefit plan liability adjustments net gain, (tax) benefit	2	0
Benefit plan liability adjustments prior service cost, (tax) benefit	(90)	0
Reclassification adjustment of benefit plan prior service cost included in net income, (tax) benefit	4	17
Reclassification adjustment of benefit plan liabilities actuarial gain (loss), (tax) benefit	$ (85)	$ (192)

Condensed Consolidated Balance Sheets (unaudited) Statement - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Current assets:
Cash and cash equivalents	$ 17,641	$ 7,841	$ 12,397
Restricted cash and equivalents	2	2	6,846
Accounts receivable, net	203,625	177,573	168,783
Materials, supplies and fuel	66,187	88,478	64,189
Derivative assets, current	1,846	717	1,630
Income tax receivable, net	1,826	1,460	0
Deferred income tax assets, net, current	25,780	18,889	38,196
Regulatory assets, current	62,946	24,451	23,422
Other current assets	24,563	25,877	28,260
Total current assets	404,416	345,288	343,723
Investments	16,916	16,697	16,545
Property, plant and equipment	4,318,194	4,259,445	3,977,704
Less accumulated depreciation and depletion	(1,298,398)	(1,269,148)	(1,210,833)
Total property, plant and equipment, net	3,019,796	2,990,297	2,766,871
Other assets:
Goodwill	353,396	353,396	353,396
Intangible assets, net	3,342	3,397	3,565
Derivative assets, non-current	0	0	0
Regulatory assets, non-current	138,173	138,197	181,119
Other assets, non-current	28,925	27,906	21,367
Total other assets, non-current	523,836	522,896	559,447
TOTAL ASSETS	3,964,964	3,875,178	3,686,586
Current liabilities:
Accounts payable	149,681	130,416	82,437
Accrued liabilities	145,973	151,277	140,230
Derivative liabilities, current	3,498	3,474	89,112
Accrued income tax, net	0	0	1,157
Regulatory liabilities, current	583	10,727	19,020
Notes payable	100,000	82,500	245,000
Current maturities of long-term debt	0	0	104,637
Total current liabilities	399,735	378,394	681,593
Long-term debt, net of current maturities	1,396,949	1,396,948	936,477
Deferred credits and other liabilities:
Deferred income tax liabilities, net, non-current	466,856	432,287	367,502
Derivative liabilities, non-current	4,805	5,614	15,237
Regulatory liabilities, non-current	116,793	109,429	126,573
Benefit plan liabilities	113,324	111,479	172,353
Other deferred credits and other liabilities	129,083	133,279	125,958
Total deferred credits and other liabilities	830,861	792,088	807,623
Commitments and contingencies (See Notes 7, 8, 13 and 14)
Stockholders’ equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 44,666,953; 44,550,239; and 44,482,304 shares, respectively	44,667	44,550	44,482
Additional paid-in capital	742,016	742,344	735,000
Retained earnings	570,963	540,244	519,184
Treasury stock, at cost – 37,038; 50,877; and 41,606 shares, respectively	(1,638)	(1,968)	(1,549)
Accumulated other comprehensive income (loss)	(18,589)	(17,422)	(36,224)
Total stockholders’ equity	1,337,419	1,307,748	1,260,893
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,964,964	$ 3,875,178	$ 3,686,586

Condensed Consolidated Balance Sheets (unaudited) Parantheticals - $ / shares	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Common Stock, Par Per Share	$ 1.00	$ 1.00	$ 1.00
Common Stock, Shares, Issued	44,666,953	44,550,239	44,482,304
Treasury Stock, Shares	37,038	50,877	41,606
Common Stock, Shares Authorized	100,000,000	100,000,000	100,000,000
Common Stock, Shares, Outstanding	44,629,915	44,499,362	44,440,698

Condensed Consoldiated Statement of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating activities:
Net income (loss) available for common stock	$ 48,118	$ 43,197
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	36,083	34,781
Deferred financing cost amortization	568	1,095
Stock compensation	3,716	3,778
Unrealized (gain) loss on interest rate swaps, net	0	(7,456)
Deferred income taxes	25,953	20,541
Employee benefit plans	3,703	5,548
Other adjustments, net	5,190	7,087
Changes in certain operating assets and liabilities:
Materials, supplies and fuel	22,291	18,519
Accounts receivable, unbilled revenue and other operating assets	(78,576)	(5,323)
Accounts payable and other current liabilities	29,074	(13,637)
Other operating activities, net	1,978	1,102
Net cash provided by operating activities	98,098	109,232
Investing activities:
Property, plant and equipment additions	(83,609)	(63,939)
Other investing activities	(3,220)	1,030
Net cash provided by (used in) investing activities	(86,829)	(62,909)
Financing activities:
Dividends paid on common stock	(17,399)	(16,882)
Common stock issued	881	2,426
Short-term borrowings - issuances	86,800	78,500
Short-term borrowings - repayments	(69,300)	(110,500)
Long-term debt - repayments	0	(1,737)
Other financing activities	(2,451)	(1,195)
Net cash provided by (used in) financing activities	(1,469)	(49,388)
Net change in cash and cash equivalents	9,800	(3,065)
Cash and Cash Equivalents:
Cash and cash equivalents, beginning of period	7,841	15,462
Cash and cash equivalents, end of period	$ 17,641	$ 12,397

Management's Statement	3 Months Ended
Management's Statement	Mar. 31, 2014
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 2013 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, 2014, December 31, 2013, and March 31, 2013 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. 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, 2014 and March 31, 2013, and our financial condition as of March 31, 2014, December 31, 2013, and March 31, 2013, 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. Recently Issued and Adopted Accounting Standards We have implemented all new accounting pronouncements that are in effect and may impact our financial statements and do not believe that there are any other new accounting pronouncements that have been issued that might have a material impact on our financial position, results of operations, or cash flows.

Business Segment Information

3 Months Ended

Mar. 31, 2014

Segment Reporting Information, Additional Information [Abstract]

Business Segment Disclosure [Text Block]

BUSINESS SEGMENT INFORMATION

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



Three Months Ended March 31, 2014	External Operating Revenue		Inter-company Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	178,095	$	4,007		$	14,575
Gas	259,337		—			24,698
Non-regulated Energy:
Power Generation	1,269		21,079			8,073
Coal Mining	6,618		8,880			2,464
Oil and Gas	14,850		—			(2,022		)
Corporate activities	—		—			330
Inter-company eliminations	—		(33,966		)	—
Total	$	460,169	$	—		$	48,118



Three Months Ended March 31, 2013	External Operating Revenue		Inter-company Operating Revenue			Net Income (Loss)
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
Inter-company eliminations	—		(31,058		)	3
Total	$	380,671	$	—		$	43,197

__________


(a)	Net income (loss) includes a $4.8 million after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 on certain interest rate swaps.

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



Total Assets (net of inter-company eliminations) as of:	March 31, 2014		December 31, 2013		March 31, 2013
Utilities:
Electric ^(a)	$	2,572,616	$	2,525,947	$	2,367,014
Gas	842,660		805,617		752,468
Non-regulated Energy:
Power Generation^(a)	90,643		95,692		115,708
Coal Mining	74,523		78,825		82,839
Oil and Gas	295,083		288,366		255,786
Corporate activities	89,439		80,731		112,771
Total assets	$	3,964,964	$	3,875,178	$	3,686,586

__________


(a)	The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under 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

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+ Details

Accounts Receivable

3 Months Ended

Mar. 31, 2014

Receivables [Abstract]

Accounts Receivable [Text Block]

ACCOUNTS RECEIVABLE

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, 2014	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	53,733	$	20,063	$	(690	)	$	73,106
Gas Utilities	77,982		35,791		(814		)	112,959
Power Generation	1,340		—		—			1,340
Coal Mining	2,616		—		—			2,616
Oil and Gas	10,920		—		(13		)	10,907
Corporate	2,697		—		—			2,697
Total	$	149,288	$	55,854	$	(1,517	)	$	203,625



	Accounts		Unbilled		Less Allowance for			Accounts
December 31, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	52,437	$	23,823	$	(666	)	$	75,594
Gas Utilities	49,162		41,195		(558		)	89,799
Power Generation	1,722		—		—			1,722
Coal Mining	1,711		—		—			1,711
Oil and Gas	8,156		—		(13		)	8,143
Corporate	604		—		—			604
Total	$	113,792	$	65,018	$	(1,237	)	$	177,573



	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

- 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 + Details

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Notes)

3 Months Ended

Mar. 31, 2014

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets and Liabilities [Text Block]

REGULATORY ACCOUNTING

We had the following regulatory assets and liabilities (in thousands):



	Maximum	As of		As of		As of
	Amortization (in years)	March 31, 2014		December 31, 2013		March 31, 2013
Regulatory assets
Deferred energy and fuel cost adjustments - current^(a)	1	$	23,935	$	16,775	$	16,815
Deferred gas cost adjustments and gas price derivatives^(a)	7	42,925		12,366		8,264
AFUDC^(b)	45	12,349		12,315		12,335
Employee benefit plans ^(c)	13	65,833		67,059		115,564
Environmental^(a)	subject to approval	1,317		1,800		1,793
Asset retirement obligations^(a)	44	3,271		3,266		3,252
Bond issue cost^(a)	24	3,383		3,419		3,526
Renewable energy standard adjustment ^(a)	5	16,088		14,186		16,325
Flow through accounting^(c)	35	21,837		20,916		17,308
Other regulatory assets^(a)	15	10,181		10,546		9,359
		$	201,119	$	162,648	$	204,541

Regulatory liabilities
Deferred energy and gas costs^(a)	1	$	6,485	$	11,708	$	21,463
Employee benefit plans^(c)	13	34,355		34,431		60,214
Cost of removal^(a)	44	67,640		64,970		56,517
Other regulatory liabilities^(c)	25	8,896		9,047		7,399
		$	117,376	$	120,156	$	145,593

__________


(a)	Recovery of costs, but not allowed a rate of return.


(b)	In addition to recovery of costs, we are allowed a rate of return.


(c)	In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively.

Materials, Supplies and Fuel

3 Months Ended

Mar. 31, 2014

Inventory, Net [Abstract]

Materials, Supplies and Fuel [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, 2014		December 31, 2013		March 31, 2013
Materials and supplies	$	50,727	$	50,196	$	50,401
Fuel - Electric Utilities	7,218		6,213		8,445
Natural gas in storage held for distribution	8,242		32,069		5,343
Total materials, supplies and fuel	$	66,187	$	88,478	$	64,189

Earnings Per Share

3 Months Ended

Mar. 31, 2014

Earnings Per Share [Abstract]

Earnings Per Share [Text Block]

EARNINGS PER SHARE

A reconciliation of share amounts used to compute Earnings (loss) per share in the accompanying Condensed Consolidated Statements of Income (loss) is as follows (in thousands):



	Three Months Ended March 31,
	2014		2013

Net Income (loss) available for common stock	$	48,118	$	43,197

Weighted average shares - basic	44,330		44,053
Dilutive effect of:
Equity compensation	224		259
Weighted average shares - diluted	44,554		44,312

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,
	2014	2013
Equity compensation	46	40
Anti-dilutive shares	46	40

Notes Payable

3 Months Ended

Mar. 31, 2014

Debt Disclosure [Abstract]

Notes Payable and Long-term Debt [Text Block]

NOTES PAYABLE

We had the following notes payable outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2014				December 31, 2013				March 31, 2013
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	100,000	$	27,700	$	82,500	$	22,100	$	95,000	$	36,500
Term Loan due June 2013	—		—		—		—		150,000		—
Total	$	100,000	$	27,700	$	82,500	$	22,100	$	245,000	$	36,500

The term loan for $150 million was repaid on June 21, 2013.

Debt Covenants

Our Revolving Credit Facility and our new Term Loan require compliance with the following financial covenant at the end of each quarter:



	As of March 31, 2014	Covenant Requirement
Recourse Leverage Ratio	55%	Less than	65	%

As of March 31, 2014, we were in compliance with this covenant.

Risk Management Activities

3 Months Ended

Mar. 31, 2014

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 2013 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 in crude oil and natural gas reserves and production; and our fuel procurement for certain of our gas-fired generation assets; and


•	Interest rate risk associated with our variable rate debt.

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, 2014, our credit exposure included an $0.8 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 rated companies, cooperative utilities and federal agencies. Our derivative and hedging activities recorded in the accompanying Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Income (Loss) and Condensed Consolidated Statements of Comprehensive Income (Loss) are detailed below and in Note 9.

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 in the accompanying Condensed Consolidated Balance Sheets and the ineffective portion, if any, is reported in Revenue in the accompanying Condensed Consolidated Statements of Income (Loss).

The contract or notional amounts, terms of our commodity derivatives, and the derivative balances for our Oil and Gas segment reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of:



	March 31, 2014				December 31, 2013				March 31, 2013
	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)	442,500		8,296,250		412,500		7,082,500		522,000		10,633,000
Maximum terms in months ^(b)	1		1		3		1		9		6
Derivative assets, current	$	—	$	—	$	55	$	—	$	821	$	287
Derivative assets, non-current	$	—	$	—	$	—	$	—	$	—	$	—
Derivative liabilities, current	$	—	$	—	$	—	$	—	$	250	$	1,188
Derivative liabilities, non-current	$	—	$	—	$	—	$	—	$	—	$	—

__________


(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 market prices at March 31, 2014, a $3.2 million loss 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 prices fluctuate.

Utilities

The operations of our utilities, including natural gas sold by our Gas Utilities and natural gas used for Electric Utility generation plants or those plants under power purchase agreements where our Electric Utilities must provide the generation fuel (tolling agreements), 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, net of balance sheet offsetting as permitted by GAAP. 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 the accompanying Condensed Consolidated Balance Sheets in accordance with state commission guidelines. Accordingly, the hedging activity is recognized in the Condensed Consolidated Statements of Income (Loss) 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 Utilities were as follows, as of:



	March 31, 2014		December 31, 2013		March 31, 2013
	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)
Natural gas futures purchased	16,140,000	80	17,930,000	84	13,180,000	80
Natural gas options purchased	1,320,000	12	3,890,000	8	440,000	5
Natural gas basis swaps purchased	14,575,000	69	14,785,000	60	11,350,000	69

We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheets as of (in thousands):



	March 31, 2014		December 31, 2013		March 31, 2013
Derivative assets, current	$	1,846	$	662	$	522
Derivative assets, non-current	$	—	$	—	$	—
Derivative liabilities, non-current	$	—	$	—	$	—
Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	4,420	$	7,567	$	4,315

Financing Activities

We entered into floating-to-fixed interest rate swap agreements to reduce our exposure to interest rate fluctuations associated with our floating rate debt obligations. The contract or notional amounts, terms of our interest rate swaps and the interest rate swaps balances reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of:



	March 31, 2014			December 31, 2013			March 31, 2013
	Interest Rate Swaps^(a)			Interest Rate Swaps^(a)			Interest Rate Swaps^(b)			De-designated Interest Rate Swaps^(c)
Notional	$	75,000		$	75,000		$	150,000		$	250,000
Weighted average fixed interest rate	4.97		%	4.97		%	5.04		%	5.67		%
Maximum terms in years	2.75			3.00			3.75			0.75
Derivative liabilities, current	$	3,498		$	3,474		$	6,982		$	80,692
Derivative liabilities, non-current	$	4,805		$	5,614		$	15,237		$	—

__________


(a)	These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related swaps.

(b)

At March 31, 2013, $75 million of these interest rate swaps were designated to borrowings on our Revolving Credit Facility and $75 million were designated to borrowings on our project financing debt at Black Hills Wyoming. These swaps are priced using three-month LIBOR, matching the floating portion of the related debt. The portion of the swaps that were designated to Black Hills Wyoming were settled during the fourth quarter of 2013 upon repayment of the Black Hills Wyoming project financing.


(c)	These swaps were settled during the fourth quarter of 2013.

Based on March 31, 2014, market interest rates and balances related to our interest rate swaps, a loss of approximately $3.5 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.

Cash Flow Hedges

The impacts of cash flow hedges on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):



Three Months Ended March 31, 2014
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	$	(91	)	Interest expense	$	(894	)		$	—
Commodity derivatives	(3,473		)	Revenue	(311		)		—
Total	$	(3,564	)		$	(1,205	)		$	—



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	)		$	—

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

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+ Details

Fair Value Measurements

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Measurement Disclosures [Text Block]

FAIR VALUE MEASUREMENTS

Derivative Financial Instruments

The accounting guidance for fair value measurements requires certain disclosures about assets and liabilities measured at fair value. This guidance establishes a hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value. 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, 8 and 9 to the Consolidated Financial Statements included in our 2013 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 when 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 using the market approach and can 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 using the market approach with 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 a Level 2 disclosure.

Utilities Segments:

•

The commodity contracts for our Utilities Segments, 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 because 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 a 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. Amounts included in cash collateral and counterparty netting in the following tables represent the impact of legally enforceable master netting agreements that allow us to settle positive and negative positions, netting of asset and liability positions permitted in accordance with accounting standards for offsetting as well as cash collateral posted with the same counterparties.

The following tables set forth by level within the fair value hierarchy our gross assets and gross liabilities and related offsetting as permitted by GAAP that were accounted for at fair value on a recurring basis for derivative instruments. A discussion of fair value of financial instruments is included in Note 10:



	As of March 31, 2014
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		7		—		(7		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		490		—		(490		)	—
Commodity derivatives — Utilities	—		3,226		—		(1,380		)	1,846
Total	$	—	$	3,723	$	—	$	(1,877	)	$	1,846

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		1,983		—		(1,983		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		2,114		—		(2,114		)	—
Commodity derivatives — Utilities	—		6,919		—		(6,919		)	—
Interest rate swaps	—		8,303		—		—			8,303
Total	$	—	$	19,319	$	—	$	(11,016	)	$	8,303



	As of December 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		130		—		(75		)	55
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		815		—		(815		)	—
Commodity derivatives —Utilities	—		3,030		—		(2,368		)	662

Total	$	—	$	3,975	$	—	$	(3,258	)	$	717

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		1,229		—		(1,229		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		531		—		(531		)	—
Commodity derivatives — Utilities	—		9,100		—		(9,100		)	—
Interest rate swaps	—		9,088		—		—			9,088
Total	$	—	$	19,948	$	—	$	(10,860	)	$	9,088



	As of March 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
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
Total	$	—	$	3,239	$	—	$	(1,609	)	$	1,630

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

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 reflecting 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 impact of legally enforceable master netting agreements that allow us to settle positive and negative positions; however, the amounts do not include net cash collateral on deposit in margin accounts at March 31, 2014, December 31, 2013, and March 31, 2013, 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 8.

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



As of March 31, 2014
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	30	$	—
Commodity derivatives	Derivative assets — non-current	466		—
Commodity derivatives	Derivative liabilities — current	—		3,187
Commodity derivatives	Derivative liabilities — non-current	—		910
Interest rate swaps	Derivative liabilities — current	—		3,498
Interest rate swaps	Derivative liabilities — non-current	—		4,805
Total derivatives designated as hedges		$	496	$	12,400

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	1,846	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		5,539
Total derivatives not designated as hedges		$	1,846	$	5,539



As of December 31, 2013
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	248	$	—
Commodity derivatives	Derivative assets — non-current	698		—
Commodity derivatives	Derivative liabilities — current	—		1,541
Commodity derivatives	Derivative liabilities — non-current	—		219
Interest rate swaps	Derivative liabilities — current	—		3,474
Interest rate swaps	Derivative liabilities — non-current	—		5,614
Total derivatives designated as hedges		$	946	$	10,848

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	662	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		6,732
Total derivatives not designated as hedges		$	662	$	6,732



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

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value of Financial Instrument Disclosures [Text Block]

FAIR VALUE OF FINANCIAL INSTRUMENTS

The estimated fair values of our financial instruments, excluding derivatives which are presented in Note 9, were as follows (in thousands) as of:



	March 31, 2014				December 31, 2013				March 31, 2013
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents ^(a)	$	17,641	$	17,641	$	7,841	$	7,841	$	12,397	$	12,397
Restricted cash and equivalents ^(a)	$	2	$	2	$	2	$	2	$	6,846	$	6,846
Notes payable ^(a)	$	100,000	$	100,000	$	82,500	$	82,500	$	245,000	$	245,000
Long-term debt, including current maturities ^(b)	$	1,396,949	$	1,541,727	$	1,396,948	$	1,491,422	$	1,041,114	$	1,208,909

__________


(a)	Carrying value approximates fair 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 + Details

Other Comprehensive Income

3 Months Ended

Mar. 31, 2014

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

Comprehensive Income (Loss) Note [Text Block]

OTHER COMPREHENSIVE INCOME (LOSS)

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



	Location on the Condensed Consolidated Statements of Income (Loss)	Amount Reclassified from AOCI
		Three Months Ended
		March 31, 2014			March 31, 2013
Gains (losses) on cash flow hedges:
Interest rate swaps	Interest expense	$	894		$	1,796
Commodity contracts	Revenue	311			(1,092		)
		1,205			704
Income tax	Income tax benefit (expense)	(425		)	(236		)
Reclassification adjustments related to cash flow hedges, net of tax		$	780		$	468

Amortization of defined benefit plans:
Prior service cost	Utilities - Operations and maintenance	$	(25	)	$	(31	)
	Non-regulated energy operations and maintenance	12			(32		)

Actuarial gain (loss)	Utilities - Operations and maintenance	157			421
	Non-regulated energy operations and maintenance	85			274
		229			632
Income tax	Income tax benefit (expense)	(81		)	(175		)
Reclassification adjustments related to defined benefit plans, net of tax		$	148		$	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, 2012	$	(15,713	)	$	(19,775	)	$	(35,488	)
Other comprehensive income (loss), net of tax	(1,193		)	457			(736		)
Balance as of March 31, 2013	$	(16,906	)	$	(19,318	)	$	(36,224	)

Balance as of December 31, 2013	$	(7,133	)	$	(10,289	)	$	(17,422	)
Other comprehensive income (loss), net of tax	(1,478		)	311			(1,167		)
Balance as of March 31, 2014	$	(8,611	)	$	(9,978	)	$	(18,589	)

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: 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=28358780&loc=d3e637-108580

Reference 8: 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=28358780&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Supplemental Cash Flow Information

3 Months Ended

Mar. 31, 2014

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosure of Cash Flows [Text Block]

SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION

Supplemental disclosures of cash flow for the three months ended are as follows (in thousands):



	Three Months Ended
	March 31, 2014			March 31, 2013

Non-cash investing and financing activities from continuing operations—
Property, plant and equipment acquired with accrued liabilities	$	40,939		$	31,780
Increase (decrease) in capitalized assets associated with asset retirement obligations	$	(2,785	)	$	—

Cash (paid) refunded during the period for continuing operations—
Interest (net of amounts capitalized)	$	(11,452	)	$	(12,768	)
Income taxes, net	$	4		$	(4,656	)

Employee Benefit Plans Employee Benefit Plans (Notes)

3 Months Ended

Mar. 31, 2014

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,
	2014			2013
Service cost	$	1,362		$	1,608
Interest cost	3,963			3,825
Expected return on plan assets	(4,516		)	(4,654		)
Prior service cost	16			16
Net loss (gain)	1,201			3,062
Net periodic benefit cost	$	2,026		$	3,857

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,
	2014			2013
Service cost	$	425		$	419
Interest cost	479			417
Expected return on plan assets	(21		)	(20		)
Prior service cost (benefit)	(107		)	(125		)
Net loss (gain)	40			121
Net periodic benefit cost	$	816		$	812

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,
	2014		2013
Service cost	$	374	$	348
Interest cost	362		332
Prior service cost	1		1
Net loss (gain)	124		198
Net periodic benefit cost	$	861	$	879

Contributions

We anticipate that we will make contributions to the benefit plans during 2014 and 2015. Contributions to the Defined Benefit Pension Plans are cash contributions made directly to the Pension Plan Trust accounts. Contributions to the Healthcare and Supplemental Plan 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, 2014		Contributions Anticipated for 2014		Contributions Anticipated for 2015
Defined Benefit Pension Plans	$	—	$	—	$	2,806
Non-pension Defined Benefit Postretirement Healthcare Plans	$	956	$	2,868	$	3,822
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	373	$	1,118	$	1,494

Commitments and Contingencies

3 Months Ended

Mar. 31, 2014

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 from those previously disclosed in Note 18 of our Notes to the Consolidated Financial Statements in our 2013 Annual Report on Form 10-K except for those described below.

Natural Gas Delivery Agreement

In 2012, we entered into a ten-year gas gathering and processing contract for natural gas production from our properties in the Piceance Basin in Colorado, under which we pay a gathering fee per Mcf. The contract requires us to deliver a minimum of 20,000 Mcf per day. This agreement became effective in first quarter of 2014 upon completion of the processing infrastructure capable of handling the committed volumes. We believe that our reserves dedicated to the gathering system, and the projected volumes are adequate to satisfy our delivery commitments under this agreement.

Other Commitments

Construction of Cheyenne Prairie, a 132 MW natural gas-fired electric generating facility jointly owned by Cheyenne Light and Black Hills Power is expected to cost approximately $222 million. Construction is expected to be completed by September 30, 2014. As of March 31, 2014, committed contracts for equipment purchases and for construction were 100% and 83% complete, respectively.

Oil Creek Fire

On June 29, 2012, a forest and grassland fire occurred in the western Black Hills of Wyoming. A state fire investigator concluded that the fire was caused by the failure of a transmission structure owned, operated and maintained by Black Hills Power. On April 16, 2013, a lawsuit was filed in the United States District Court for the District of Wyoming, which forty-seven plaintiffs have now joined, asserting claims for damages against Black Hills Power. The claims include allegations of negligence, negligence per se, common law nuisance, and trespass. Although not currently included in the lawsuit, Black Hills Power also received written damage claims from an additional landowner and from the State of Wyoming. Altogether the claims seek recovery for fire suppression, reclamation and rehabilitation costs, damage to fencing and other personal property, alleged injury to timber, grass or hay, livestock and related operations, and diminished value of real estate, for a current total amount of $16 million. In addition to claims for these compensatory damages, the lawsuit seeks recovery of punitive damages. Our investigation of the cause and origin of the fire is ongoing. We have denied and will vigorously defend all claims arising out of the fire, pending the completion of our investigation. We cannot predict the outcome of our investigation, the viability of alleged claims or the outcome of the litigation.

Civil litigation of this kind, however, is likely to lead to settlement negotiations, including negotiations prompted by pre-trial civil court procedures. We believe such negotiations would effect a settlement of all claims. Regardless of whether the litigation is determined at trial or through settlement, we expect to incur significant investigation, legal and expert services expenses associated with the litigation. In order to limit our exposure to losses due to civil liability claims, and related litigation expense, we maintain insurance coverage above a $1.0 million deductible. We expect this coverage to limit our exposure, and we will pursue recoveries to the maximum extent available under the policies. Based upon information currently available, we believe that a loss associated with settlement of pending claims is probable. Accordingly, as of March 31, 2014, we recorded a loss contingency liability related to these claims, and we recorded a receivable for costs we believe are reimbursable and probable of recovery under our insurance coverage. Both of these entries reflect our reasonable estimate of probable future litigation expense and settlement costs; we did not base these contingencies on any determination that it is probable we would be found liable for these claims were they to be litigated.

Given the uncertainty of litigation, however, a loss related to the fire, the litigation and related claims in excess of the loss we have determined to be probable is reasonably possible. However, we cannot reasonably estimate the amount of such possible loss because our investigation is ongoing, damage claims are currently incomplete or undocumented, and there are significant factual and legal issues to be resolved. Further claims may be presented by these and other parties. Based upon information currently available, however, management does not expect the outcome of the claims to have a material adverse effect upon our consolidated financial condition, results of operations or cash flows.

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, 2014, 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, 2014:


•	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, 2014, the restricted net assets at our Utilities Group were approximately $94 million.

Business Segment Information Business Segment Information (Tables)

3 Months Ended

Mar. 31, 2014

Segment Reporting Information, Additional Information [Abstract]

Schedule of Segment Reporting Information [Table Text Block]

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



Three Months Ended March 31, 2014	External Operating Revenue		Inter-company Operating Revenue			Net Income (Loss)
Utilities:
Electric	$	178,095	$	4,007		$	14,575
Gas	259,337		—			24,698
Non-regulated Energy:
Power Generation	1,269		21,079			8,073
Coal Mining	6,618		8,880			2,464
Oil and Gas	14,850		—			(2,022		)
Corporate activities	—		—			330
Inter-company eliminations	—		(33,966		)	—
Total	$	460,169	$	—		$	48,118



Three Months Ended March 31, 2013	External Operating Revenue		Inter-company Operating Revenue			Net Income (Loss)
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
Inter-company eliminations	—		(31,058		)	3
Total	$	380,671	$	—		$	43,197

__________


(a)	Net income (loss) includes a $4.8 million after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 on certain interest rate swaps.

Reconciliation of Assets from Segment to Consolidated [Table Text Block]

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



Total Assets (net of inter-company eliminations) as of:	March 31, 2014		December 31, 2013		March 31, 2013
Utilities:
Electric ^(a)	$	2,572,616	$	2,525,947	$	2,367,014
Gas	842,660		805,617		752,468
Non-regulated Energy:
Power Generation^(a)	90,643		95,692		115,708
Coal Mining	74,523		78,825		82,839
Oil and Gas	295,083		288,366		255,786
Corporate activities	89,439		80,731		112,771
Total assets	$	3,964,964	$	3,875,178	$	3,686,586

__________


(a)	The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under accounting for a capital lease.

Accounts Receivable Accounts Receivable (Tables)

3 Months Ended

Mar. 31, 2014

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, 2014	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	53,733	$	20,063	$	(690	)	$	73,106
Gas Utilities	77,982		35,791		(814		)	112,959
Power Generation	1,340		—		—			1,340
Coal Mining	2,616		—		—			2,616
Oil and Gas	10,920		—		(13		)	10,907
Corporate	2,697		—		—			2,697
Total	$	149,288	$	55,854	$	(1,517	)	$	203,625



	Accounts		Unbilled		Less Allowance for			Accounts
December 31, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
Electric Utilities	$	52,437	$	23,823	$	(666	)	$	75,594
Gas Utilities	49,162		41,195		(558		)	89,799
Power Generation	1,722		—		—			1,722
Coal Mining	1,711		—		—			1,711
Oil and Gas	8,156		—		(13		)	8,143
Corporate	604		—		—			604
Total	$	113,792	$	65,018	$	(1,237	)	$	177,573



	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

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2014

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets and Liabilities [Table Text Block]

We had the following regulatory assets and liabilities (in thousands):



	Maximum	As of		As of		As of
	Amortization (in years)	March 31, 2014		December 31, 2013		March 31, 2013
Regulatory assets
Deferred energy and fuel cost adjustments - current^(a)	1	$	23,935	$	16,775	$	16,815
Deferred gas cost adjustments and gas price derivatives^(a)	7	42,925		12,366		8,264
AFUDC^(b)	45	12,349		12,315		12,335
Employee benefit plans ^(c)	13	65,833		67,059		115,564
Environmental^(a)	subject to approval	1,317		1,800		1,793
Asset retirement obligations^(a)	44	3,271		3,266		3,252
Bond issue cost^(a)	24	3,383		3,419		3,526
Renewable energy standard adjustment ^(a)	5	16,088		14,186		16,325
Flow through accounting^(c)	35	21,837		20,916		17,308
Other regulatory assets^(a)	15	10,181		10,546		9,359
		$	201,119	$	162,648	$	204,541

Regulatory liabilities
Deferred energy and gas costs^(a)	1	$	6,485	$	11,708	$	21,463
Employee benefit plans^(c)	13	34,355		34,431		60,214
Cost of removal^(a)	44	67,640		64,970		56,517
Other regulatory liabilities^(c)	25	8,896		9,047		7,399
		$	117,376	$	120,156	$	145,593

__________


(a)	Recovery of costs, but not allowed a rate of return.


(b)	In addition to recovery of costs, we are allowed a rate of return.


(c)	In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively.

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

3 Months Ended

Mar. 31, 2014

Inventory, Net [Abstract]

Materials, Supplies and Fuel [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, 2014		December 31, 2013		March 31, 2013
Materials and supplies	$	50,727	$	50,196	$	50,401
Fuel - Electric Utilities	7,218		6,213		8,445
Natural gas in storage held for distribution	8,242		32,069		5,343
Total materials, supplies and fuel	$	66,187	$	88,478	$	64,189

Earnings Per Share Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2014

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 in the accompanying Condensed Consolidated Statements of Income (loss) is as follows (in thousands):



	Three Months Ended March 31,
	2014		2013

Net Income (loss) available for common stock	$	48,118	$	43,197

Weighted average shares - basic	44,330		44,053
Dilutive effect of:
Equity compensation	224		259
Weighted average shares - diluted	44,554		44,312

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,
	2014	2013
Equity compensation	46	40
Anti-dilutive shares	46	40

Notes Payable Schedule Of Short Term Debt (Tables)

3 Months Ended

Mar. 31, 2014

Debt Disclosure [Abstract]

Schedule of Short-term Debt [Table Text Block]

We had the following notes payable outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:



	March 31, 2014				December 31, 2013				March 31, 2013
	Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
Revolving Credit Facility	$	100,000	$	27,700	$	82,500	$	22,100	$	95,000	$	36,500
Term Loan due June 2013	—		—		—		—		150,000		—
Total	$	100,000	$	27,700	$	82,500	$	22,100	$	245,000	$	36,500

Credit Facility and Short Term Debt Covenants [Table Text Block]

Our Revolving Credit Facility and our new Term Loan require compliance with the following financial covenant at the end of each quarter:



	As of March 31, 2014	Covenant Requirement
Recourse Leverage Ratio	55%	Less than	65	%

Risk Management Activities Risk Management Activities (Tables)

3 Months Ended

Mar. 31, 2014

Derivative [Line Items]

Schedule of Derivative Instruments [Table Text Block]

The contract or notional amounts, terms of our interest rate swaps and the interest rate swaps balances reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of:



	March 31, 2014			December 31, 2013			March 31, 2013
	Interest Rate Swaps^(a)			Interest Rate Swaps^(a)			Interest Rate Swaps^(b)			De-designated Interest Rate Swaps^(c)
Notional	$	75,000		$	75,000		$	150,000		$	250,000
Weighted average fixed interest rate	4.97		%	4.97		%	5.04		%	5.67		%
Maximum terms in years	2.75			3.00			3.75			0.75
Derivative liabilities, current	$	3,498		$	3,474		$	6,982		$	80,692
Derivative liabilities, non-current	$	4,805		$	5,614		$	15,237		$	—

__________


(a)	These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related swaps.

(b)


(c)	These swaps were settled during the fourth quarter of 2013.

Derivative Instruments, Gain (Loss) [Table Text Block]

The impacts of cash flow hedges on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):



Three Months Ended March 31, 2014
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	$	(91	)	Interest expense	$	(894	)		$	—
Commodity derivatives	(3,473		)	Revenue	(311		)		—
Total	$	(3,564	)		$	(1,205	)		$	—



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	)		$	—

Oil and Gas [Member]

Derivative [Line Items]

Schedule of Derivative Instruments [Table Text Block]



	March 31, 2014				December 31, 2013				March 31, 2013
	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)	442,500		8,296,250		412,500		7,082,500		522,000		10,633,000
Maximum terms in months ^(b)	1		1		3		1		9		6
Derivative assets, current	$	—	$	—	$	55	$	—	$	821	$	287
Derivative assets, non-current	$	—	$	—	$	—	$	—	$	—	$	—
Derivative liabilities, current	$	—	$	—	$	—	$	—	$	250	$	1,188
Derivative liabilities, non-current	$	—	$	—	$	—	$	—	$	—	$	—

__________


(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]

Schedule of Derivative Instruments [Table Text Block]

We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheets as of (in thousands):



	March 31, 2014		December 31, 2013		March 31, 2013
Derivative assets, current	$	1,846	$	662	$	522
Derivative assets, non-current	$	—	$	—	$	—
Derivative liabilities, non-current	$	—	$	—	$	—
Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	4,420	$	7,567	$	4,315

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 Utilities were as follows, as of:



	March 31, 2014		December 31, 2013		March 31, 2013
	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)	Notional (MMBtus)	Maximum Term (months)
Natural gas futures purchased	16,140,000	80	17,930,000	84	13,180,000	80
Natural gas options purchased	1,320,000	12	3,890,000	8	440,000	5
Natural gas basis swaps purchased	14,575,000	69	14,785,000	60	11,350,000	69

- 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 5
-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41641-113959

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959

Reference 4: 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 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 1A
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

Reference 7: 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 8: 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 9: 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 10: 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

Reference 11: 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=26873400&loc=d3e23780-122690

+ Details

Fair Value Measurements Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

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



	As of March 31, 2014
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		7		—		(7		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		490		—		(490		)	—
Commodity derivatives — Utilities	—		3,226		—		(1,380		)	1,846
Total	$	—	$	3,723	$	—	$	(1,877	)	$	1,846

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		1,983		—		(1,983		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		2,114		—		(2,114		)	—
Commodity derivatives — Utilities	—		6,919		—		(6,919		)	—
Interest rate swaps	—		8,303		—		—			8,303
Total	$	—	$	19,319	$	—	$	(11,016	)	$	8,303



	As of December 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		130		—		(75		)	55
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		815		—		(815		)	—
Commodity derivatives —Utilities	—		3,030		—		(2,368		)	662

Total	$	—	$	3,975	$	—	$	(3,258	)	$	717

Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—	$	—	$	—	$	—		$	—
Basis Swaps -- Oil	—		1,229		—		(1,229		)	—
Options -- Gas	—		—		—		—			—
Basis Swaps -- Gas	—		531		—		(531		)	—
Commodity derivatives — Utilities	—		9,100		—		(9,100		)	—
Interest rate swaps	—		9,088		—		—			9,088
Total	$	—	$	19,948	$	—	$	(10,860	)	$	9,088



	As of March 31, 2013
	Level 1		Level 2		Level 3		Cash Collateral and Counterparty Netting			Total
	(in thousands)
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
Total	$	—	$	3,239	$	—	$	(1,609	)	$	1,630

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

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, 2014
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	30	$	—
Commodity derivatives	Derivative assets — non-current	466		—
Commodity derivatives	Derivative liabilities — current	—		3,187
Commodity derivatives	Derivative liabilities — non-current	—		910
Interest rate swaps	Derivative liabilities — current	—		3,498
Interest rate swaps	Derivative liabilities — non-current	—		4,805
Total derivatives designated as hedges		$	496	$	12,400

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	1,846	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		5,539
Total derivatives not designated as hedges		$	1,846	$	5,539



As of December 31, 2013
	Balance Sheet Location	Fair Value of Asset Derivatives		Fair Value of Liability Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current	$	248	$	—
Commodity derivatives	Derivative assets — non-current	698		—
Commodity derivatives	Derivative liabilities — current	—		1,541
Commodity derivatives	Derivative liabilities — non-current	—		219
Interest rate swaps	Derivative liabilities — current	—		3,474
Interest rate swaps	Derivative liabilities — non-current	—		5,614
Total derivatives designated as hedges		$	946	$	10,848

Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current	$	662	$	—
Commodity derivatives	Derivative assets — non-current	—		—
Commodity derivatives	Derivative liabilities — current	—		—
Commodity derivatives	Derivative liabilities — non-current	—		6,732
Total derivatives not designated as hedges		$	662	$	6,732



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

Fair Value of Financial Instruments Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments [Table Text Block]

The estimated fair values of our financial instruments, excluding derivatives which are presented in Note 9, were as follows (in thousands) as of:



	March 31, 2014				December 31, 2013				March 31, 2013
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Cash and cash equivalents ^(a)	$	17,641	$	17,641	$	7,841	$	7,841	$	12,397	$	12,397
Restricted cash and equivalents ^(a)	$	2	$	2	$	2	$	2	$	6,846	$	6,846
Notes payable ^(a)	$	100,000	$	100,000	$	82,500	$	82,500	$	245,000	$	245,000
Long-term debt, including current maturities ^(b)	$	1,396,949	$	1,541,727	$	1,396,948	$	1,491,422	$	1,041,114	$	1,208,909

__________


(a)	Carrying value approximates fair 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.

Other Comprehensive Income Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2014

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

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

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



	Location on the Condensed Consolidated Statements of Income (Loss)	Amount Reclassified from AOCI
		Three Months Ended
		March 31, 2014			March 31, 2013
Gains (losses) on cash flow hedges:
Interest rate swaps	Interest expense	$	894		$	1,796
Commodity contracts	Revenue	311			(1,092		)
		1,205			704
Income tax	Income tax benefit (expense)	(425		)	(236		)
Reclassification adjustments related to cash flow hedges, net of tax		$	780		$	468

Amortization of defined benefit plans:
Prior service cost	Utilities - Operations and maintenance	$	(25	)	$	(31	)
	Non-regulated energy operations and maintenance	12			(32		)

Actuarial gain (loss)	Utilities - Operations and maintenance	157			421
	Non-regulated energy operations and maintenance	85			274
		229			632
Income tax	Income tax benefit (expense)	(81		)	(175		)
Reclassification adjustments related to defined benefit plans, net of tax		$	148		$	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, 2012	$	(15,713	)	$	(19,775	)	$	(35,488	)
Other comprehensive income (loss), net of tax	(1,193		)	457			(736		)
Balance as of March 31, 2013	$	(16,906	)	$	(19,318	)	$	(36,224	)

Balance as of December 31, 2013	$	(7,133	)	$	(10,289	)	$	(17,422	)
Other comprehensive income (loss), net of tax	(1,478		)	311			(1,167		)
Balance as of March 31, 2014	$	(8,611	)	$	(9,978	)	$	(18,589	)

Supplemental Cash Flow Information Supplmental Cash Flow Information (Tables)

3 Months Ended

Mar. 31, 2014

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosures of Cash Flows [Table Text Block]

Supplemental disclosures of cash flow for the three months ended are as follows (in thousands):



	Three Months Ended
	March 31, 2014			March 31, 2013

Non-cash investing and financing activities from continuing operations—
Property, plant and equipment acquired with accrued liabilities	$	40,939		$	31,780
Increase (decrease) in capitalized assets associated with asset retirement obligations	$	(2,785	)	$	—

Cash (paid) refunded during the period for continuing operations—
Interest (net of amounts capitalized)	$	(11,452	)	$	(12,768	)
Income taxes, net	$	4		$	(4,656	)

Employee Benefit Plans Schedule Of Defined Benefit Plans Disclosure (Tables)

3 Months Ended

Mar. 31, 2014

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,
	2014			2013
Service cost	$	1,362		$	1,608
Interest cost	3,963			3,825
Expected return on plan assets	(4,516		)	(4,654		)
Prior service cost	16			16
Net loss (gain)	1,201			3,062
Net periodic benefit cost	$	2,026		$	3,857

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,
	2014			2013
Service cost	$	425		$	419
Interest cost	479			417
Expected return on plan assets	(21		)	(20		)
Prior service cost (benefit)	(107		)	(125		)
Net loss (gain)	40			121
Net periodic benefit cost	$	816		$	812

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,
	2014		2013
Service cost	$	374	$	348
Interest cost	362		332
Prior service cost	1		1
Net loss (gain)	124		198
Net periodic benefit cost	$	861	$	879

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, 2014		Contributions Anticipated for 2014		Contributions Anticipated for 2015
Defined Benefit Pension Plans	$	—	$	—	$	2,806
Non-pension Defined Benefit Postretirement Healthcare Plans	$	956	$	2,868	$	3,822
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	373	$	1,118	$	1,494

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

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Segment Reporting Information [Line Items]

Revenue, Net

$ 460,169

$ 380,671

Net Income (Loss)

48,118

43,197

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

4,800

Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

(33,966)

(31,058)

Net Income (Loss)

Corporate, Non-Segment [Member]

Segment Reporting Information [Line Items]

Revenue, Net

Net Income (Loss)

330

5,699

^[1]

Consolidation, Eliminations [Member]

Segment Reporting Information [Line Items]

Revenue, Net

Electric Utilities [Member]

Segment Reporting Information [Line Items]

Revenue, Net

178,095

158,483

Net Income (Loss)

14,575

12,356

Electric Utilities [Member] | Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

4,007

4,147

Gas Utilities [Member]

Segment Reporting Information [Line Items]

Revenue, Net

259,337

199,812

Net Income (Loss)

24,698

18,483

Gas Utilities [Member] | Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

Power Generation [Member]

Segment Reporting Information [Line Items]

Revenue, Net

1,269

1,022

Net Income (Loss)

8,073

5,644

Power Generation [Member] | Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

21,079

19,338

Coal Mining [Member]

Segment Reporting Information [Line Items]

Revenue, Net

6,618

6,010

Net Income (Loss)

2,464

1,065

Coal Mining [Member] | Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

8,880

7,573

Oil and Gas [Member]

Segment Reporting Information [Line Items]

Revenue, Net

14,850

15,344

Net Income (Loss)

(2,022)

(53)

Oil and Gas [Member] | Intersegment Elimination [Member]

Segment Reporting Information [Line Items]

Revenue, Net

$ 0

[1]	income (loss) includes a $4.8 million after-tax non-cash mark-to-market gain for the three months ended March 31, 2013 on certain interest rate swaps.

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

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

$ 3,964,964

$ 3,875,178

$ 3,686,586

Corporate, Non-Segment [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

89,439

80,731

112,771

Electric Utilities [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

^[1]

2,572,616

2,525,947

2,367,014

Gas Utilities [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

842,660

805,617

752,468

Power Generation [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

^[1]

90,643

95,692

115,708

Coal Mining [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

74,523

78,825

82,839

Oil and Gas [Member]

Segment Reporting, Asset Reconciling Item [Line Items]

Assets

$ 295,083

$ 288,366

$ 255,786

[1]

The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under accounting for a capital lease.

Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	$ (1,517)	$ (1,237)	$ (1,393)
Accounts receivable, net	203,625	177,573	168,783
Corporate, Non-Segment [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	2,697	604	1,026
Electric Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(690)	(666)	(623)
Accounts receivable, net	73,106	75,594	68,864
Gas Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(814)	(558)	(751)
Accounts receivable, net	112,959	89,799	86,712
Power Generation [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	1,340	1,722	3
Coal Mining [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	2,616	1,711	1,857
Oil and Gas [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	(13)	(13)	(19)
Accounts receivable, net	10,907	8,143	10,321
Billed Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	149,288	113,792	120,146
Billed Revenues [Member] \| Corporate, Non-Segment [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	2,697	604	1,026
Billed Revenues [Member] \| Electric Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	53,733	52,437	47,896
Billed Revenues [Member] \| Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	77,982	49,162	59,024
Billed Revenues [Member] \| Power Generation [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	1,340	1,722	3
Billed Revenues [Member] \| Coal Mining [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	2,616	1,711	1,857
Billed Revenues [Member] \| Oil and Gas [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	10,920	8,156	10,340
Unbilled Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	55,854	65,018	50,030
Unbilled Revenues [Member] \| Corporate, Non-Segment [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] \| Electric Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	20,063	23,823	21,591
Unbilled Revenues [Member] \| Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	35,791	41,195	28,439
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

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets

$ 201,119

$ 162,648

$ 204,541

Regulatory Liabilities

$ 117,376

120,156

145,593

Deferred energy and fuel cost adjustments

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Liabilities Amortization Period (in years)

P1Y

Regulatory Liabilities

^[1]

$ 6,485

11,708

21,463

Employee benefit plans

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Liabilities Amortization Period (in years)

P13Y

Regulatory Liabilities

^[2]

$ 34,355

34,431

60,214

Cost of removal

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Liabilities Amortization Period (in years)

P44Y

Regulatory Liabilities

^[1]

$ 67,640

64,970

56,517

Other regulatory liabilities

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Liabilities Amortization Period (in years)

P25Y

Regulatory Liabilities

^[2]

$ 8,896

9,047

7,399

Deferred energy and fuel cost adjustments

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P1Y

Regulatory Assets

^[1]

$ 23,935

16,775

16,815

Deferred gas cost adjustments and gas price derivatives

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P7Y

Regulatory Assets

^[1]

$ 42,925

12,366

8,264

Allowance For Funds Used During Construction

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P45Y

Regulatory Assets

^[3]

$ 12,349

12,315

12,335

Employee benefit plans

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P13Y

Regulatory Assets

^[2]

$ 65,833

67,059

115,564

Environmental

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

subject to approval

Regulatory Assets

^[1]

$ 1,317

1,800

1,793

Asset retirement obligations

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P44Y

Regulatory Assets

^[1]

$ 3,271

3,266

3,252

Bond issue cost

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P24Y

Regulatory Assets

^[1]

$ 3,383

3,419

3,526

Renewable energy standard adjustment

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P5Y

Regulatory Assets

^[1]

$ 16,088

14,186

16,325

Flow through accounting

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P35Y

Regulatory Assets

^[2]

$ 21,837

20,916

17,308

Other regulatory assets

Schedule Of Regulatory Assets And Liabilities [Line Items]

Regulatory Assets Amortization Period (in years)

P15Y

Regulatory Assets

^[1]

$ 10,181

$ 10,546

$ 9,359

[1]	Recovery of costs, but not allowed a rate of return.
[2]	In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively.
[3]	In addition to recovery of costs, we are allowed a rate of return.

Materials, Supplies and Fuel (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Inventory, Net [Abstract]
Materials and supplies	$ 50,727	$ 50,196	$ 50,401
Fuel - Electric Utilities	7,218	6,213	8,445
Natural gas in storage held for distribution	8,242	32,069	5,343
Total materials, supplies and fuel	$ 66,187	$ 88,478	$ 64,189

Earnings Per Share Basic to Dilutive EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (loss) available for common stock	$ 48,118	$ 43,197
Weighted average shares - basic	44,330	44,053
Dilutive Effect on Basic Earnings Per Share [Abstract]
Equity compensation, shares	224	259
Weighted average shares - diluted	44,554	44,312

Earnings Per Share Anti-dilutive shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	46	40
Equity compensation [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	46	40

Notes Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Line of Credit Facility [Line Items]
Notes payable	$ 100,000	$ 82,500	$ 245,000
Letters of Credit Outstanding	27,700	22,100	36,500
Loans Payable [Member]
Line of Credit Facility [Line Items]
Notes payable	0	0	150,000
Letters of Credit Outstanding	0	0	0
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Notes payable	100,000	82,500	95,000
Letters of Credit Outstanding	$ 27,700	$ 22,100	$ 36,500
Debt Disclosure [Abstract]
Recourse Leverage Ratio	55.00%
Recourse Leverage Ratio, Maximum Allowed, Covenant	65.00%

Notes Payable Replacement of Notes Payable (Details) $ in Millions	12 Months Ended
	Dec. 31, 2013 USD ($)
Loans Payable [Member]
Extinguishment of Debt, Amount	$ 150

Risk Management Activities (Details)
$ in Thousands

3 Months Ended

12 Months Ended

Mar. 31, 2014

USD ($)

bbl

MMBTU

Mar. 31, 2013

USD ($)

bbl

MMBTU

Dec. 31, 2013

USD ($)

bbl

MMBTU

Derivative [Line Items]

Credit Exposure, Non-Investment Grade Company

$ 800

Derivative assets, current

1,846

$ 1,630

$ 717

Derivative assets, non-current

Derivative liabilities, current

3,498

89,112

3,474

Derivative liabilities, non-current

4,805

15,237

5,614

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

Derivative [Line Items]

Derivative liabilities, current

3,498

6,982

3,474

Derivative liabilities, non-current

4,805

15,237

5,614

Derivative, Notional Amount

$ 75,000

^[1]

$ 150,000

^[2]

$ 75,000

^[1]

Weighted Average Fixed Interest Rate

4.97%

5.04%

4.97%

Derivative, Remaining Maturity

2 years 9 months

3 years 9 months

3 years

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

$ (3,500)

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

Derivative [Line Items]

Derivative liabilities, current

$ 80,692

Derivative liabilities, non-current

Derivative, Notional Amount

^[3]

$ 250,000

Weighted Average Fixed Interest Rate

5.67%

Derivative, Remaining Maturity

9 months

Oil and Gas [Member]

Derivative [Line Items]

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

(3,200)

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

Derivative [Line Items]

Derivative, Notional Amount

$ 75,000

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

Derivative [Line Items]

Derivative assets, current

1,846

522

$ 662

Derivative assets, non-current

Derivative liabilities, non-current

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

$ 4,420

$ 4,315

$ 7,567

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

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

16,140,000

13,180,000

17,930,000

Derivative, Remaining Maturity

80 months

84 months

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

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

1,320,000

440,000

3,890,000

Derivative, Remaining Maturity

12 months

5 months

8 months

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

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

14,575,000

11,350,000

14,785,000

Derivative, Remaining Maturity

69 months

60 months

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

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | bbl

^[4]

442,500

522,000

412,500

Maximum terms in months - Hedged in Cash Flow Hedge

^[5]

1 month

9 months

3 months

Derivative assets, current

$ 0

$ 821

$ 55

Derivative assets, non-current

Derivative liabilities, current

250

Derivative liabilities, non-current

$ 0

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

Derivative [Line Items]

Derivative, Nonmonetary Notional Amount | MMBTU

^[4]

8,296,250

10,633,000

7,082,500

Maximum terms in months - Hedged in Cash Flow Hedge

^[5]

1 month

6 months

1 month

Derivative assets, current

$ 0

$ 287

$ 0

Derivative assets, non-current

Derivative liabilities, current

1,188

Derivative liabilities, non-current

$ 0

Corporate, Non-Segment [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Derivative, Notional Amount

$ 75,000

[1]	These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related swaps.
[2]	At March 31, 2013, $75 million of these interest rate swaps were designated to borrowings on our Revolving Credit Facility and $75 million were designated to borrowings on our project financing debt at Black Hills Wyoming. These swaps are priced using three-month LIBOR, matching the floating portion of the related debt. The portion of the swaps that were designated to Black Hills Wyoming were settled during the fourth quarter of 2013 upon repayment of the Black Hills Wyoming project financing.
[3]	These swaps were settled during the fourth quarter of 2013.
[4]	Crude oil in Bbls, natural gas in MMBtus.
[5]	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.

Risk Management Activities Hedging Activities (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	$ (3,564)	$ (2,778)
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	(1,205)	(704)
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	(91)	(19)
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	0
Interest Rate Swap [Member] \| Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	(894)	(1,796)
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	(3,473)	(2,759)
Commodity Contract [Member] \| Sales Revenue, Goods, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	(311)	1,092
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	$ 0	$ 0

Fair Value Measurements Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Fair Value, Transfers Between Level 1 and Level 2, Description and Policy [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0	$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0	0	0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0	0
Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas, Distribution [Member] \| Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	3,723	3,975	3,239
Liabilities, Fair Value Disclosure	19,319	19,948	119,015
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	8,303	9,088	108,871
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	71
Derivative Liabilities	0	0	396
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	7	130	836
Derivative Liabilities	1,983	1,229	670
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	490	815	435
Derivative Liabilities	2,114	531	3,216
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas, Distribution [Member] \| Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	3,226	3,030	1,897
Derivative Liabilities	6,919	9,100	5,862
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0	0
Liabilities, Fair Value Disclosure	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas, Distribution [Member] \| Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Netting [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	(1,877)	(3,258)	(1,609)
Liabilities, Fair Value Disclosure	(11,016)	(10,860)	(14,666)
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0	0	(5,960)
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	(11)
Derivative Liabilities	0	0	(204)
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	(7)	(75)	(75)
Derivative Liabilities	(1,983)	(1,229)	(612)
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	(490)	(815)	(148)
Derivative Liabilities	(2,114)	(531)	(2,028)
Netting [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas, Distribution [Member] \| Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	(1,380)	(2,368)	(1,375)
Derivative Liabilities	(6,919)	(9,100)	(5,862)
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	1,846	717	1,630
Liabilities, Fair Value Disclosure	8,303	9,088	104,349
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	8,303	9,088	102,911
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	60
Derivative Liabilities	0	0	192
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Crude Oil [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	55	761
Derivative Liabilities	0	0	58
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Commodity Option [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	0
Derivative Liabilities	0	0	0
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas [Member] \| Basis Swap [Member] \| Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0	287
Derivative Liabilities	0	0	1,188
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Natural Gas, Distribution [Member] \| Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1,846	662	522
Derivative Liabilities	$ 0	$ 0	$ 0

Fair Value Measurements Fair Value Measurements Balance Sheet Location (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	$ 496	$ 946	$ 1,038
Derivative Liability, Fair Value, Net	12,400	10,848	26,443
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	1,846	662	2,201
Derivative Liability, Fair Value, Net	5,539	6,732	92,572
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Assets, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	30	248	832
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Assets, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	466	698	206
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	3,187	1,541	3,110
Commodity Contract [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	910	219	1,114
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Assets, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,846	662	2,201
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Assets, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0	0
Derivative Asset, Fair Value, Gross Liability	0	0	0
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	0	0
Derivative Liability, Fair Value, Gross Liability	0	0	58
Commodity Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	5,539	6,732	5,862
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	3,498	3,474	6,982
Interest Rate Swap [Member] \| Designated as Hedging Instrument [Member] \| Derivative Liabilities, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	$ 4,805	$ 5,614	15,237
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
Derivative Liability, Fair Value, Gross Liability			86,652
Interest Rate Swap [Member] \| Not Designated as Hedging Instrument [Member] \| Derivative Liabilities, Non-current [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset			0
Derivative Liability, Fair Value, Gross Liability			$ 0

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

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

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

Cash and cash equivalents

$ 17,641

$ 7,841

$ 12,397

Restricted cash and equivalents

6,846

Notes payable

100,000

82,500

245,000

Reported Value Measurement [Member]

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

Cash and cash equivalents

17,641

7,841

12,397

Restricted cash and equivalents

6,846

Notes payable

100,000

82,500

245,000

Long-term debt, including current maturities

1,396,949

1,396,948

1,041,114

Estimate of Fair Value Measurement [Member]

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

Cash and Cash Equivalents, Fair Value

^[1]

17,641

7,841

12,397

Restricted Cash and equivalents, Fair Value

^[1]

6,846

Notes payable, Fair Value

^[1]

100,000

82,500

245,000

Long-term debt, including current maturities, Fair Value

^[2]

$ 1,541,727

$ 1,491,422

$ 1,208,909

[1]	Carrying value approximates fair 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.

Other Comprehensive Income Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 17,860	$ 23,672
Revenue	460,169	380,671
Utilities - Operating and Maintenance	71,227	65,690
Non-regulated energy operations and maintenance	22,332	21,329
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	73,485	64,860
Income tax benefit (expense)	(25,366)	(21,577)
Cash Flow Hedging [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	1,205	704
Income tax benefit (expense)	(425)	(236)
Net income (loss) available for common stock	780	468
Cash Flow Hedging [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member] \| Interest Rate Contract [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense	894	1,796
Cash Flow Hedging [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member] \| Commodity Contract [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Revenue	311	(1,092)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Utilities - Operating and Maintenance	(25)	(31)
Non-regulated energy operations and maintenance	12	(32)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Utilities - Operating and Maintenance	157	421
Non-regulated energy operations and maintenance	85	274
Accumulated Defined Benefit Plans Adjustment [Member] \| Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	229	632
Income tax benefit (expense)	(81)	(175)
Net income (loss) available for common stock	$ 148	$ 457

Other Comprehensive Income Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (18,589)	$ (36,224)	$ (17,422)	$ (35,488)
Other Comprehensive Income (Loss), Net of Tax	(1,167)	(736)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(8,611)	(16,906)	(7,133)	(15,713)
Other Comprehensive Income (Loss), Net of Tax	(1,478)	(1,193)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(9,978)	(19,318)	$ (10,289)	$ (19,775)
Other Comprehensive Income (Loss), Net of Tax	$ 311	$ 457

- Definition

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

+ References + Details

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Non-cash Investing and Financing Activities from Continuing Operations [Abstract]
Property, plant and equipment acquired wtih accrued liabilities	$ 40,939	$ 31,780
Increase (decrease) in capitalized assets associated with asset retirement obligations	(2,785)	0
Cash (paid) refunded during the period for continuing operations [Abstract]
Interest (net of amounts capitalized)	(11,452)	(12,768)
Income taxes, net	$ 4	$ (4,656)

Employee Benefit Plans Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 1,362	$ 1,608
Interest cost	3,963	3,825
Expected return on plan assets	(4,516)	(4,654)
Prior service cost (benefit)	16	16
Net loss (gain)	1,201	3,062
Net periodic benefit cost	2,026	3,857
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	0
Estimated Future Employer Contributions in Current Fiscal Year	0
Estimated Future Employer Contributions in Next Fiscal Year	2,806
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	425	419
Interest cost	479	417
Expected return on plan assets	(21)	(20)
Prior service cost (benefit)	(107)	(125)
Net loss (gain)	40	121
Net periodic benefit cost	816	812
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	956
Estimated Future Employer Contributions in Current Fiscal Year	2,868
Estimated Future Employer Contributions in Next Fiscal Year	3,822
Other Pension Plan, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	374	348
Interest cost	362	332
Prior service cost (benefit)	1	1
Net loss (gain)	124	198
Net periodic benefit cost	861	$ 879
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	373
Estimated Future Employer Contributions in Current Fiscal Year	1,118
Estimated Future Employer Contributions in Next Fiscal Year	$ 1,494

Commitments and Contingencies Commitments and Contingencies (Details) - Cheyenne Prairie [Member] $ in Millions	3 Months Ended
	Mar. 31, 2014 USD ($)
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 222
Equipment [Member]
Long-term Purchase Commitment [Line Items]
Long Term Purchase Commitment, Percentage Committed	100.00%
Construction Contracts [Member]
Long-term Purchase Commitment [Line Items]
Long Term Purchase Commitment, Percentage Committed	83.00%

Commitments and Contingencies Legal Proceedings (Details) - Electric Utilities [Member] - Loss from Catastrophes [Member] $ in Millions	3 Months Ended
	Mar. 31, 2014 USD ($)
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	$ 16.0
Insurance Coverage Deductible Per Occurrence	$ 1.0

Commitments and Contingencies Dividend Restrictions (Details) $ in Millions	Mar. 31, 2014 USD ($)
Utilities Group [Member]
Related Party Transaction [Line Items]
Restricted Net Assets for Subsidiaries	$ 94