Black Hills (BKH) 10-Q 2 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
	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	31-Mar-14	'
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

Condensed Statements of Income (unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	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_Stateme

Condensed Consolidated Statement of Comprehensive Income (unaudited) Statement (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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

Condensed Consolidated Balance Sheets (unaudited) Statement (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_Balance1

Condensed Consolidated Balance Sheets (unaudited) Parantheticals (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Common Stock, Par Per Share	$1	$1	$1
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_Stateme

Condensed Consoldiated Statement of Cash Flows (unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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

Managements_Statement

Management's Statement	3 Months Ended
	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

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			Inter-company				Net Income (Loss)
			Operating			Operating
			Revenue			Revenue
	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			Inter-company				Net Income (Loss)
			Operating			Operating
			Revenue			Revenue
	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:	31-Mar-14			31-Dec-13				31-Mar-13
	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	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
	31-Mar-14	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
	31-Dec-13	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
	31-Mar-13	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_Liabilit

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)	31-Mar-14		31-Dec-13		31-Mar-13
	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	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:
		31-Mar-14		31-Dec-13		31-Mar-13
	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	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

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:
		31-Mar-14					31-Dec-13				31-Mar-13
		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

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:
		31-Mar-14							31-Dec-13							31-Mar-13
		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:
		31-Mar-14					31-Dec-13					31-Mar-13
		Notional			Maximum		Notional			Maximum		Notional			Maximum
		(MMBtus)			Term		(MMBtus)			Term		(MMBtus)			Term
					(months)					(months)					(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):
		31-Mar-14			31-Dec-13			31-Mar-13
	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:
		31-Mar-14				31-Dec-13				31-Mar-13
		Interest Rate				Interest Rate				Interest Rate			De-designated
		Swaps (a)				Swaps (a)				Swaps (b)			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				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				Location		Amount of				Location of		Amount of
		Gain/(Loss)				of Gain/(Loss)		Reclassified				Gain/(Loss)		Gain/(Loss)
		Recognized				Reclassified		Gain/(Loss)				Recognized		Recognized in
		in AOCI				from AOCI		from AOCI				in Income		Income on
		Derivative				into Income		into Income				on Derivative		Derivative
		(Effective				(Effective		(Effective				(Ineffective		(Ineffective
		Portion)				Portion)		Portion)				Portion)		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				Location		Amount of				Location of		Amount of
		Gain/(Loss)				of Gain/(Loss)		Reclassified				Gain/(Loss)		Gain/(Loss)
		Recognized				Reclassified		Gain/(Loss)				Recognized		Recognized in
		in AOCI				from AOCI		from AOCI				in Income		Income on
		Derivative				into Income		into Income				on Derivative		Derivative
		(Effective				(Effective		(Effective				(Ineffective		(Ineffective
		Portion)				Portion)		Portion)				Portion)		Portion)
Interest rate swaps		$	(19	)		Interest expense		$	(1,796	)				$	—
Commodity derivatives		(2,759		)		Revenue		1,092						—
Total		$	(2,778	)				$	(704	)				$	—

Fair_Value_Measurements

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			Total
										Netting
		(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			Total
										Netting
		(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			Total
										Netting
		(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			Fair Value
			of Asset			of Liability
			Derivatives			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			Fair Value
			of Asset			of Liability
			Derivatives			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			Fair Value
			of Asset			of Liability
			Derivatives			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_Instru

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:
		31-Mar-14				31-Dec-13				31-Mar-13
		Carrying		Fair Value		Carrying		Fair Value		Carrying		Fair Value
		Amount				Amount				Amount
	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	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
			31-Mar-14			31-Mar-13
	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	)

Supplemental_Cash_Flow_Informa

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
		31-Mar-14			31-Mar-13
	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_Employe

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

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_B

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			Inter-company				Net Income (Loss)
			Operating			Operating
			Revenue			Revenue
	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			Inter-company				Net Income (Loss)
			Operating			Operating
			Revenue			Revenue
	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:	31-Mar-14			31-Dec-13				31-Mar-13
	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_R

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
	31-Mar-14	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
	31-Dec-13	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
	31-Mar-13	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_Liabilit1

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)	31-Mar-14		31-Dec-13		31-Mar-13
	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_Ma

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:
		31-Mar-14		31-Dec-13		31-Mar-13
	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_Pe

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_Shor

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:
		31-Mar-14					31-Dec-13				31-Mar-13
		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_Ris

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:
		31-Mar-14				31-Dec-13				31-Mar-13
		Interest Rate				Interest Rate				Interest Rate			De-designated
		Swaps (a)				Swaps (a)				Swaps (b)			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				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.
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				Location		Amount of				Location of		Amount of
			Gain/(Loss)				of Gain/(Loss)		Reclassified				Gain/(Loss)		Gain/(Loss)
			Recognized				Reclassified		Gain/(Loss)				Recognized		Recognized in
			in AOCI				from AOCI		from AOCI				in Income		Income on
			Derivative				into Income		into Income				on Derivative		Derivative
			(Effective				(Effective		(Effective				(Ineffective		(Ineffective
			Portion)				Portion)		Portion)				Portion)		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				Location		Amount of				Location of		Amount of
			Gain/(Loss)				of Gain/(Loss)		Reclassified				Gain/(Loss)		Gain/(Loss)
			Recognized				Reclassified		Gain/(Loss)				Recognized		Recognized in
			in AOCI				from AOCI		from AOCI				in Income		Income on
			Derivative				into Income		into Income				on Derivative		Derivative
			(Effective				(Effective		(Effective				(Ineffective		(Ineffective
			Portion)				Portion)		Portion)				Portion)		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]	'
	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:
		31-Mar-14							31-Dec-13							31-Mar-13
		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):
		31-Mar-14			31-Dec-13			31-Mar-13
	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:
		31-Mar-14					31-Dec-13					31-Mar-13
		Notional			Maximum		Notional			Maximum		Notional			Maximum
		(MMBtus)			Term		(MMBtus)			Term		(MMBtus)			Term
					(months)					(months)					(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

Fair_Value_Measurements_Fair_V

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]	'
	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			Total
										Netting
		(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			Total
										Netting
		(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			Total
										Netting
		(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			Fair Value
				of Asset			of Liability
				Derivatives			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			Fair Value
				of Asset			of Liability
				Derivatives			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			Fair Value
				of Asset			of Liability
				Derivatives			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_Instru1

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:
		31-Mar-14				31-Dec-13				31-Mar-13
		Carrying		Fair Value		Carrying		Fair Value		Carrying		Fair Value
		Amount				Amount				Amount
	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_Oth

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
			31-Mar-14			31-Mar-13
	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_Informa1

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
		31-Mar-14			31-Mar-13
	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_Schedul

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_I

Business Segment Information Information Relating to Segment Statement of Income (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]	'	'
Revenue, Net	$460,169,000	$380,671,000
Net Income (Loss)	48,118,000	43,197,000
Mark-to-market gain (loss) on certain interest rate swaps, net of tax	'	4,800,000
Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	-33,966,000	-31,058,000
Net Income (Loss)	0	3,000
Corporate, Non-Segment [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	0	0
Net Income (Loss)	330,000	5,699,000	[1]
Consolidation, Eliminations [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	0	0
Electric Utilities [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	178,095,000	158,483,000
Net Income (Loss)	14,575,000	12,356,000
Electric Utilities [Member] | Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	4,007,000	4,147,000
Gas Utilities [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	259,337,000	199,812,000
Net Income (Loss)	24,698,000	18,483,000
Gas Utilities [Member] | Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	0	0
Power Generation [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	1,269,000	1,022,000
Net Income (Loss)	8,073,000	5,644,000
Power Generation [Member] | Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	21,079,000	19,338,000
Coal Mining [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	6,618,000	6,010,000
Net Income (Loss)	2,464,000	1,065,000
Coal Mining [Member] | Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	8,880,000	7,573,000
Oil and Gas [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	14,850,000	15,344,000
Net Income (Loss)	-2,022,000	-53,000
Oil and Gas [Member] | Intersegment Elimination [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Revenue, Net	$0	$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_S

Business Segment Information Segment and Corporate Assets (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Thousands, unless otherwise specified
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	2,572,616	[1]	2,525,947	[1]	2,367,014	[1]
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	90,643	[1]	95,692	[1]	115,708	[1]
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

Accounts Receivable (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_Liabilit2

Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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	6,485	[1]	11,708	[1]	21,463	[1]
Employee benefit plans	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Liabilities Amortization Period (in years)	'P13Y		'		'
Regulatory Liabilities	34,355	[2]	34,431	[2]	60,214	[2]
Cost of removal	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Liabilities Amortization Period (in years)	'P44Y		'		'
Regulatory Liabilities	67,640	[1]	64,970	[1]	56,517	[1]
Other regulatory liabilities	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Liabilities Amortization Period (in years)	'P25Y		'		'
Regulatory Liabilities	8,896	[2]	9,047	[2]	7,399	[2]
Deferred energy and fuel cost adjustments	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P1Y		'		'
Regulatory Assets	23,935	[1]	16,775	[1]	16,815	[1]
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	42,925	[1]	12,366	[1]	8,264	[1]
Allowance For Funds Used During Construction	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P45Y		'		'
Regulatory Assets	12,349	[3]	12,315	[3]	12,335	[3]
Employee benefit plans	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P13Y		'		'
Regulatory Assets	65,833	[2]	67,059	[2]	115,564	[2]
Environmental	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'subject to approval		'		'
Regulatory Assets	1,317	[1]	1,800	[1]	1,793	[1]
Asset retirement obligations	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P44Y		'		'
Regulatory Assets	3,271	[1]	3,266	[1]	3,252	[1]
Bond issue cost	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P24Y		'		'
Regulatory Assets	3,383	[1]	3,419	[1]	3,526	[1]
Renewable energy standard adjustment	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P5Y		'		'
Regulatory Assets	16,088	[1]	14,186	[1]	16,325	[1]
Flow through accounting	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P35Y		'		'
Regulatory Assets	21,837	[2]	20,916	[2]	17,308	[2]
Other regulatory assets	'		'		'
Schedule Of Regulatory Assets And Liabilities [Line Items]	'		'		'
Regulatory Assets Amortization Period (in years)	'P15Y		'		'
Regulatory Assets	$10,181	[1]	$10,546	[1]	$9,359	[1]
[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_De

Materials, Supplies and Fuel (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_Di

Earnings Per Share Basic to Dilutive EPS (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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_Antidilutiv

Earnings Per Share Anti-dilutive shares (Details)	3 Months Ended
In Thousands, unless otherwise specified	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

Notes Payable (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_N

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

Risk_Management_Activities_Det

Risk Management Activities (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Derivative [Line Items]	'		'		'
Credit Exposure, Non-Investment Grade Company	$800,000		'		'
Derivative assets, current	1,846,000		1,630,000		717,000
Derivative assets, non-current	0		0		0
Derivative liabilities, current	3,498,000		89,112,000		3,474,000
Derivative liabilities, non-current	4,805,000		15,237,000		5,614,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative liabilities, current	3,498,000		6,982,000		3,474,000
Derivative liabilities, non-current	4,805,000		15,237,000		5,614,000
Derivative, Notional Amount	75,000,000	[1]	150,000,000	[2]	75,000,000	[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	-3,500,000		'		'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative liabilities, current	'		80,692,000		'
Derivative liabilities, non-current	'		0		'
Derivative, Notional Amount	'		250,000,000	[3]	'
Weighted Average Fixed Interest Rate	'		5.67%		'
Derivative, Remaining Maturity	'		'0 years 9 months		'
Oil and Gas [Member]	'		'		'
Derivative [Line Items]	'		'		'
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	-3,200,000		'		'
Power Generation [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Notional Amount	'		75,000,000		'
Natural Gas, Distribution [Member] | Utilities Group [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative assets, current	1,846,000		522,000		662,000
Derivative assets, non-current	0		0		0
Derivative liabilities, non-current	0		0		0
Net Unrealized (Gain) Loss Included in Regulatory assets or Regulatory liabilities	4,420,000		4,315,000		7,567,000
Natural Gas, Distribution [Member] | Utilities Group [Member] | Future [Member] | Purchase Contract [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	16,140,000		13,180,000		17,930,000
Derivative, Remaining Maturity	'80 months		'80 months		'84 months
Natural Gas, Distribution [Member] | Utilities Group [Member] | Commodity Option [Member] | Purchase Contract [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	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	14,575,000		11,350,000		14,785,000
Derivative, Remaining Maturity	'69 months		'69 months		'60 months
Crude Oil [Member] | Oil and Gas [Member] | Swaps and Options [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	442,500	[4]	522,000	[4]	412,500	[4]
Maximum terms in months - Hedged in Cash Flow Hedge	'1 month	[5]	'9 months	[5]	'3 months	[5]
Derivative assets, current	0		821,000		55,000
Derivative assets, non-current	0		0		0
Derivative liabilities, current	0		250,000		0
Derivative liabilities, non-current	0		0		0
Natural Gas [Member] | Oil and Gas [Member] | Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	8,296,250	[4]	10,633,000	[4]	7,082,500	[4]
Maximum terms in months - Hedged in Cash Flow Hedge	'1 month	[5]	'6 months	[5]	'1 month	[5]
Derivative assets, current	0		287,000		0
Derivative assets, non-current	0		0		0
Derivative liabilities, current	0		1,188,000		0
Derivative liabilities, non-current	0		0		0
Corporate, Non-Segment [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Notional Amount	'		$75,000,000		'
[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_Hed

Risk Management Activities Hedging Activities (Details) (Cash Flow Hedging [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	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_V1

Fair Value Measurements Fair Value Hierarchy (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_V2

Fair Value Measurements Fair Value Measurements Balance Sheet Location (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'
Cash and cash equivalents	$17,641		$7,841		$12,397
Restricted cash and equivalents	2		2		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	2		2		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	17,641	[1]	7,841	[1]	12,397	[1]
Restricted Cash and equivalents, Fair Value	2	[1]	2	[1]	6,846	[1]
Notes payable, Fair Value	100,000	[1]	82,500	[1]	245,000	[1]
Long-term debt, including current maturities, Fair Value	$1,541,727	[2]	$1,491,422	[2]	$1,208,909	[2]
[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_Oth1

Other Comprehensive Income Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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_Acc

Other Comprehensive Income Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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	'	'

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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_Employe1

Employee Benefit Plans Employee Benefit Plans (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	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 Commitments and Contingencies (Details) (Cheyenne Prairie [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
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_1

Commitments and Contingencies Legal Proceedings (Details) (Electric Utilities [Member], Loss from Catastrophes [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Electric Utilities [Member] | Loss from Catastrophes [Member]	'
Loss Contingencies [Line Items]	'
Loss Contingency, Damages Sought, Value	$16
Insurance Coverage Deductible Per Occurrence	$1

Commitments_and_Contingencies_2

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