Black Hills (BKH) 10-Q 5 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document Information [Line Items]	'	'
Entity Registrant Name	'BLACK HILLS CORP /SD/	'
Entity Central Index Key	'0001130464	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-13	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	44,485,101
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'

Condensed_Statements_of_Income

Condensed Statements of Income (unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue	$259,907	$246,808	$920,404	$855,022
Utilities -	'	'	'	'
Fuel, purchased power and cost of gas sold	71,503	62,582	338,848	283,217
Operations and maintenance	66,061	59,398	196,728	183,721
Non-regulated energy operations and maintenance	20,484	22,466	62,703	65,774
Gain on Sale of operating assets	0	-27,285	0	-27,285
Depreciation, depletion and amortization	36,135	41,408	106,068	121,398
Taxes - property, production and severance	10,068	10,213	30,517	31,201
Impairment of long-lived asets	0	0	0	26,868
Other operating expenses	90	216	1,091	1,679
Total operating expenses	204,341	168,998	735,955	686,573
Operating income	55,566	77,810	184,449	168,449
Interest charges -	'	'	'	'
Interest expense incurred (including amortization of debt issuance costs, premiums and discounts and realized settlements on interest rate swaps)	-23,840	-27,475	-70,881	-85,151
Allowance for funds used during construction - borrowed	347	1,127	831	2,608
Capitalized interest	273	175	811	467
Unrealized gain (loss) on interest rate swaps, net	3,144	605	29,393	-2,902
Interest income	565	364	1,325	1,428
Allowance for funds used during construction - equity	85	196	327	668
Other income (expense), net	318	-287	1,197	2,073
Total other income (expense), net	-19,108	-25,295	-36,997	-80,809
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes	36,458	52,515	147,452	87,640
Equity in earnings (loss) of unconsolidated subsidiaries	0	22	-86	-12
Income tax benefit (expense)	-13,334	-17,914	-50,527	-30,057
Income (loss) from continuing operations	23,124	34,623	96,839	57,571
Income (loss) from discontinued operations, net of tax	0	-166	0	-6,810
Net income (loss) available for common stock	$23,124	$34,457	$96,839	$50,761
Earnings (loss) per share, Basic -	'	'	'	'
Income (loss) from continuing operations, per share	$0.52	$0.79	$2.19	$1.31
Income (loss) from discontinued operations, per share	$0	$0	$0	($0.16)
Total income (loss) per share, Basic	$0.52	$0.79	$2.19	$1.15
Earnings (loss) per share, Diluted -	'	'	'	'
Income (loss) from continuing operations, per share	$0.52	$0.78	$2.18	$1.31
Income (loss) from discontinued operations, per share	$0	$0	$0	($0.16)
Total income (loss) per share, Diluted	$0.52	$0.78	$2.18	$1.15
Weighted Average Number of Shares Outstanding:	'	'	'	'
Basic	44,201	43,847	44,143	43,792
Diluted	44,457	44,108	44,395	44,026
Dividends paid per share of common stock	$0.38	$0.37	$1.14	$1.11

Condensed_Consolidated_Stateme

Condensed Consolidated Statement of Comprehensive Income (unaudited) Statement (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income (loss) available for common stock	$23,124	$34,457	$96,839	$50,761
Other comprehensive income (loss), net of tax:	'	'	'	'
Fair value adjustment on derivatives designated as cash flow hedges (net of tax (expense) benefit of $964 and $1,204 for the three months ended 2013 and 2012 and $(93) and $1,092 for the nine months ended 2013 and 2012, respectively)	-2,083	-3,591	134	-3,004
Reclassification adjustments related to defined benefit plan (net of tax of $(220) for the three months ended 2013 and $(663) for the nine months ended 2013)	417	0	1,238	0
Reclassification adjustments of cash flow hedges settled and included in net income (loss) (net of tax (expense) benefit of $(586) and $13 for the three months ended 2013 and 2012 and $(1,469) and $890 for the nine months ended 2013 and 2012, respectively)	1,426	28	3,095	-1,333
Other comprehensive income (loss), net of tax	-240	-3,563	4,467	-4,337
Comprehensive income (loss) available for common stock	22,884	30,894	101,306	46,424
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Parenthetical Disclosures	'	'	'	'
Fair value adjustment of derivatives designated as cash flow hedges, (tax) benefit	964	1,204	-93	1,092
Reclassification adjustment related to defined benefit plans included in net income, (tax) benefit	-220	0	-663	0
Reclassification adjustments of cash flow hedges settled and included in net income, (tax) benefit	($586)	$13	($1,469)	$890

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (unaudited) Statement (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Thousands, unless otherwise specified
Current assets:	'	'	'
Cash and cash equivalents	$13,637	$15,462	$247,192
Restricted cash and equivalents	6,782	7,916	7,302
Accounts receivable, net	114,137	163,698	104,482
Materials, supplies and fuel	95,230	77,643	80,900
Derivative assets, current	126	3,236	16,063
Income tax receivable, net	4,539	0	11,869
Deferred income tax assets, net, current	37,163	77,231	33,681
Regulatory assets, current	30,208	31,125	24,606
Other current assets	27,075	28,795	44,823
Total current assets	328,897	405,106	570,918
Investments	16,612	16,402	16,273
Property, plant and equipment	4,152,097	3,930,772	3,950,222
Less accumulated depreciation and depletion	-1,258,450	-1,188,023	-1,253,808
Total property, plant and equipment, net	2,893,647	2,742,749	2,696,414
Other assets:	'	'	'
Goodwill	353,396	353,396	353,396
Intangible assets, net	3,453	3,620	3,675
Derivative assets, non-current	0	510	1,167
Regulatory assets, non-current	183,119	188,268	191,935
Other assets, non-current	22,116	19,420	19,850
Total other assets, non-current	562,084	565,214	570,023
TOTAL ASSETS	3,801,240	3,729,471	3,853,628
Current liabilities:	'	'	'
Accounts payable	77,077	84,422	69,138
Accrued liabilities	152,911	154,389	179,284
Derivative liabilities, current	65,944	96,541	86,509
Accrued income tax, net	0	4,936	0
Regulatory liabilities, current	14,707	13,628	10,705
Notes payable	138,300	277,000	225,000
Current maturities of long-term debt	255,694	103,973	328,310
Total current liabilities	704,633	734,889	898,946
Long-term debt, net of current maturities	955,979	938,877	942,950
Deferred credits and other liabilities:	'	'	'
Deferred income tax liabilities, net, non-current	403,772	385,908	338,194
Derivative liabilities, non-current	11,388	16,941	41,410
Regulatory liabilities, non-current	131,730	127,656	120,491
Benefit plan liabilities	169,448	167,397	167,690
Other deferred credits and other liabilities	133,341	125,294	129,630
Total deferred credits and other liabilities	849,679	823,196	797,415
Commitments and contingencies (See Notes 5, 8, 10 and 13)	'	'	'
Common stock equity:	'	'	'
Common stock $1 par value; 100,000,000 shares authorized; issued 44,532,245; 44,278,189; and 44,250,588 shares, respectively	44,532	44,278	44,251
Additional Paid in Capital	740,209	733,095	731,176
Retained earnings	539,030	492,869	478,459
Treasury stock, at cost – 47,127; 71,782; and 75,420 shares, respectively	-1,801	-2,245	-2,354
Accumulated other comprehensive income (loss)	-31,021	-35,488	-37,215
Total stockholders’ equity	1,290,949	1,232,509	1,214,317
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$3,801,240	$3,729,471	$3,853,628

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (unaudited) Parantheticals (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Common Stock, Par Per Share	$1	$1	$1
Common Stock, Shares, Issued	44,532,245	44,278,189	44,250,588
Treasury Stock, Shares	47,127	71,782	75,420
Common Stock, Shares Authorized	100,000,000	100,000,000	100,000,000
Common Stock, Shares, Outstanding	44,485,118	44,206,407	44,175,168

Condensed_Consoldiated_Stateme

Condensed Consoldiated Statement of Cash Flows (unaudited) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities:	'	'
Net income (loss) available for common stock	$96,839,000	$50,761,000
(Income) loss from discontinued operations, net of tax	0	6,810,000
Income (loss) from continuing operations	96,839,000	57,571,000
Adjustments to reconcile income (loss) from continuing operations to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	106,068,000	121,398,000
Deferred financing cost amortization	3,209,000	5,301,000
Impairment of long-lived asets	0	26,868,000
Derivative fair value adjustments	275,000	-3,522,000
Gain on Sale of operating assets	0	-27,285,000
Stock compensation	9,100,000	5,974,000
Unrealized (gain) loss on interest rate swaps, net	-29,393,000	2,902,000
Deferred income taxes	54,865,000	28,718,000
Employee benefit plans	16,644,000	15,737,000
Other adjustments, net	9,434,000	2,837,000
Changes in certain operating assets and liabilities:	'	'
Materials, supplies and fuel	-12,522,000	3,085,000
Accounts receivable, unbilled revenue and other operating assets	28,762,000	56,301,000
Accounts payable and other current liabilities	-23,774,000	-22,041,000
Contributions to defined benefit pension plans	-12,500,000	-25,000,000
Other operating activities, net	4,759,000	-361,000
Net cash provided by operating activities of continuing operations	251,766,000	248,483,000
Net cash provided by (used in) operating activities of discontinued operations	0	21,184,000
Net cash provided by operating activities	251,766,000	269,667,000
Investing activities:	'	'
Property, plant and equipment additions	-239,485,000	-261,414,000
Proceeds from sale of assets	0	268,482,000
Investment in notes receivable	0	-21,832,000
Other investing activities	2,846,000	5,057,000
Net cash provided by (used in) investing activities of continuing operations	-236,639,000	-9,707,000
Proceeds from sale of discontinued business operations	0	108,837,000
Net cash provided by (used in) investing activities of discontinued operations	0	-824,000
Net cash provided by (used in) investing activities	-236,639,000	98,306,000
Financing activities:	'	'
Dividends paid on common stock	-50,678,000	-48,904,000
Common stock issued	3,606,000	3,835,000
Short-term borrowings - issuances	269,600,000	62,453,000
Short-term borrowings - repayments	-408,300,000	-182,453,000
Long-term debt - issuances	275,000,000	0
Long-term debt - repayments	-106,180,000	-11,647,000
Other financing activities	0	-2,833,000
Net cash provided by (used in) financing activities of continuing operations	-16,952,000	-179,549,000
Net cash provided by (used in) financing activities of discontinued operations	0	0
Net cash provided by (used in) financing activities	-16,952,000	-179,549,000
Net change in cash and cash equivalents	-1,825,000	188,424,000
Cash and Cash Equivalents:	'	'
Cash and cash equivalents, beginning of period	15,462,000	58,768,000	[1]
Cash and cash equivalents, end of period	$13,637,000	$247,192,000
[1]	Includes cash of discontinued operations of $37.1 million at Dec. 31, 2011.

Managements_Statement

Management's Statement	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Management's Statement [Text Block]	'
	MANAGEMENT’S STATEMENT
	The unaudited Condensed Consolidated Financial Statements included herein have been prepared by Black Hills Corporation (together with our subsidiaries the “Company,” “us,” “we,” or “our”), pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations; however, we believe that the footnotes adequately disclose the information presented. These Condensed Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2012 Annual Report on Form 10-K filed with the SEC.
	We conduct our operations through the following reportable segments: Electric Utilities, Gas Utilities, Power Generation, Coal Mining and Oil and Gas. Our reportable segments are based on our method of internal reporting, which generally segregates the strategic business groups due to differences in products, services and regulation. All of our operations and assets are located within the United States.
	Accounting methods historically employed require certain estimates as of interim dates. The information furnished in the accompanying Condensed Consolidated Financial Statements reflects all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012 financial information and are of a normal recurring nature. Certain industries in which we operate are highly seasonal, and revenue from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Demand for electricity and natural gas is sensitive to seasonal cooling, heating and industrial load requirements, as well as changes in market price. In particular, the normal peak usage season for electric utilities is June through August while the normal peak usage season for gas utilities is November through March. Significant earnings variances can be expected between the Gas Utilities segment’s peak and off-peak seasons. Due to this seasonal nature, our results of operations for the three and nine months ended Sept. 30, 2013 and Sept. 30, 2012, and our financial condition as of Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012, are not necessarily indicative of the results of operations and financial condition to be expected as of or for any other period. All earnings per share amounts discussed refer to diluted earnings per share unless otherwise noted.
	On Feb. 29, 2012, we sold our Energy Marketing segment, which resulted in this segment being classified as discontinued operations.
	Recently Adopted Accounting Standards
	Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, ASU 2013-02
	In February 2013, the FASB issued ASU 2013-02 which requires new disclosures for items reclassified out of AOCI. ASU 2013-02 requires disclosure of (1) changes in components of other comprehensive income, (2) items reclassified out of AOCI and into net income in their entirety, the effect of the reclassification on each affected net income line item and (3) cross references to other disclosures that provide additional detail for components of other comprehensive income that are not reclassified in their entirety to net income. Disclosures are required either on the face of the statements of income or as a separate disclosure in the notes to the financial statements. The new disclosure requirements are effective for interim and annual periods beginning after Dec. 15, 2012. The adoption of this standard did not have an impact on our financial position, results of operations or cash flows. See additional disclosures in Note 7.
	Balance Sheet: Disclosure about Offsetting Assets and Liabilities, ASU 2011-11
	In December 2011, the FASB issued revised accounting guidance to amend disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting and/or similar arrangement. In addition, the revised guidance requires that certain enhanced quantitative and qualitative disclosures are made with respect to a company’s netting arrangements and/or rights of offset associated with its financial instruments and/or derivative instruments. The revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning Jan. 1, 2013. The adoption of this standard did not have an impact on our financial position, results of operations or cash flows. See additional disclosures in Note 11.
	Inclusion of the Fed Funds Effective Swap Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, ASU 2013-10
	In July 2013, the FASB issued an amendment to accounting for derivatives and hedges to permit the Fed Funds Effective Swap Rate to be used as a U.S. benchmark interest rate for hedge accounting purposes effective for new or re-designated hedging relationships entered into on or after July 17, 2013. The amendment also removed the restriction on using different benchmark rates for similar hedges. The initial adoption had no impact on our consolidated financial position, results of operations or cash flows.
	Recently Issued Accounting Pronouncements and Legislation
	Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists, ASU 2013-11
	In July 2013, the FASB issued an amendment to accounting for income taxes which provides guidance on financial statement presentation of an unrecognized tax benefit when an NOL carryforward, a similar tax loss, or a tax credit carryforward exists. The objective in issuing this amendment is to eliminate diversity in practice resulting from a lack of guidance on this topic in current GAAP. Under the amendment, an entity must present an unrecognized tax benefit, or a portion of an unrecognized tax benefit, in the financial statements as a reduction to a deferred tax asset for an NOL carryforward, a similar tax loss, or a tax credit carryforward except under certain conditions. The amendment is effective for fiscal years beginning after Dec. 15, 2013, and interim periods within those years and should be applied to all unrecognized tax benefits that exist as of the effective date. The adoption of this standard is not expected to have an impact on our financial position, results of operations or cash flows.
	Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date, ASU 2013-04
	In March 2013, the FASB issued new disclosure requirements for recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements including disclosure of the nature and amount of the obligations. The new disclosure requirements are effective for interim and annual periods beginning after Dec. 15, 2013. The amendment requires enhanced disclosures in the notes to financial statements, but will not have any other impact on our consolidated financial statements.
	Dodd-Frank Wall Street Reform and Consumer Protection Act, SEC Final Rule No. 34-67716
	In August 2012, under Dodd-Frank, the SEC adopted new requirements for companies that manufacture or contract to manufacture products that contain certain minerals and metals, known as conflict minerals. The final rule requires all issuers that file reports with the SEC and use conflict minerals to report supply chain and sourcing information on an annual basis. These new requirements will require due diligence efforts in 2013, with initial disclosure requirements beginning in May 2014. Based on our preliminary analysis, we do not believe that our products contain conflict minerals as defined by the rule; however, our assessment process to determine whether conflict minerals are necessary to the functionality or production of any of our products is not complete.
	Tangible Personal Property, IRS T.D. 9636
	In September 2013, the U.S. Treasury issued final regulations addressing the tax consequences associated with the acquisition, production and improvement of tangible property. We continue to evaluate what impact the adoption of the regulations will have on our consolidated financial statements. As of this date, we do not expect the adoption of the regulations to have a material impact on our consolidated financial statements.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Disclosure of Cash Flows [Text Block]	'
	SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
	Supplemental disclosures of cash flow for the nine months ended are as follows (in thousands):
		Nine Months Ended
		Sept. 30, 2013			Sept. 30, 2012
	Non-cash investing and financing activities from continuing operations—
	Property, plant and equipment acquired with accrued liabilities	$	47,214		$	39,303
	Increase (decrease) in capitalized assets associated with asset retirement obligations	$	—		$	3,806
	Cash (paid) refunded during the period for continuing operations—
	Interest (net of amounts capitalized)	$	(57,175	)	$	(69,901	)
	Income taxes, net	$	(4,924	)	$	425

Materials_Supplies_and_Fuel

Materials, Supplies and Fuel	9 Months Ended
	Sep. 30, 2013
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:
		Sept. 30, 2013		Dec. 31, 2012		Sept. 30, 2012
	Materials and supplies	$	50,564	$	43,397	$	43,847
	Fuel - Electric Utilities	6,384		8,589		8,289
	Natural gas in storage held for distribution	38,282		25,657		28,764
	Total materials, supplies and fuel	$	95,230	$	77,643	$	80,900

Accounts_Receivable

Accounts Receivable	9 Months Ended
	Sep. 30, 2013
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
	Sept. 30, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	49,254	$	20,153	$	(648	)	$	68,759
	Gas Utilities	20,693		11,877		(542		)	32,028
	Power Generation	3		—		—			3
	Coal Mining	2,677		—		—			2,677
	Oil and Gas	8,463		—		(19		)	8,444
	Corporate	2,226		—		—			2,226
	Total	$	83,316	$	32,030	$	(1,209	)	$	114,137
		Accounts		Unbilled		Less Allowance for			Accounts
	Dec. 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	54,482	$	23,843	$	(527	)	$	77,798
	Gas Utilities	31,495		39,962		(222		)	71,235
	Power Generation	16		—		—			16
	Coal Mining	2,247		—		—			2,247
	Oil and Gas	11,622		—		(19		)	11,603
	Corporate	799		—		—			799
	Total	$	100,661	$	63,805	$	(768	)	$	163,698
		Accounts		Unbilled		Less Allowance for			Accounts
	Sept. 30, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	46,802	$	18,441	$	(603	)	$	64,640
	Gas Utilities	18,198		9,480		(204		)	27,474
	Power Generation	4		—		—			4
	Coal Mining	1,540		—		—			1,540
	Oil and Gas	10,272		—		(105		)	10,167
	Corporate	657		—		—			657
	Total	$	77,473	$	27,921	$	(912	)	$	104,482

Notes_Payable_and_LongTerm_Deb

Notes Payable and Long-Term Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Notes Payable and Long-term Debt [Text Block]	'
	NOTES PAYABLE AND LONG-TERM DEBT
	We had the following notes payable outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:
		Sept. 30, 2013					Dec. 31, 2012				Sept. 30, 2012
		Balance Outstanding		Letters of Credit			Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
	Revolving Credit Facility	$	138,300	$	53,137		$	127,000	$	36,300	$	75,000	$	36,300
	Term Loan due June 2013	—		—			150,000		—		150,000		—
	Total	$	138,300	$	53,137		$	277,000	$	36,300	$	225,000	$	36,300
	Replacement of Notes Payable and Long-Term Term Loan
	On June 21, 2013, we entered into a new $275 million term loan expiring on June 19, 2015. The proceeds from this new term loan repaid the $150 million term loan due on June 24, 2013, the $100 million corporate term loan due on Sept. 30, 2013, and $25 million in short-term borrowing under our Revolving Credit Facility. At Sept. 30, 2013, the cost of borrowing under this new term loan was 1.3125 percent (LIBOR plus a margin of 1.125 percent). The covenants of the new term loan are substantially the same as the Revolving Credit Facility.
	Debt Covenants
	Our Revolving Credit Facility and our new Term Loan require compliance with the following financial covenant at the end of each quarter (dollars in thousands):
		As of
		Sept. 30, 2013		Covenant Requirement
	Recourse Leverage Ratio	52	%	Less than	65	%
	As of Sept. 30, 2013, we were in compliance with this covenant.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share [Text Block]	'
	EARNINGS PER SHARE
	A reconciliation of share amounts used to compute Earnings (loss) per share in the accompanying Condensed Consolidated Statements of Income (loss) is as follows (in thousands):
		Three Months Ended Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013		2012
	Income (loss) from continuing operations	$	23,124		$	34,623		$	96,839	$	57,571
	Weighted average shares - basic	44,201			43,847			44,143		43,792
	Dilutive effect of:
	Restricted stock	131			175			137		159
	Stock options	13			12			13		14
	Other dilutive effects	112			74			102		61
	Weighted average shares - diluted	44,457			44,108			44,395		44,026
	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 Sept. 30,				Nine Months Ended Sept. 30,
		2013		2012		2013	2012
	Stock options	—		77		9	101
	Restricted stock	—		61		—	53
	Other stock	—		—		—	19
	Anti-dilutive shares	—		138		9	173

Other_Comprehensive_Income

Other Comprehensive Income	9 Months Ended
	Sep. 30, 2013
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						Nine Months Ended
			Sept. 30, 2013			Sept. 30, 2012			Sept. 30, 2013			Sept. 30, 2012
	Gains (losses) on cash flow hedges:
	Interest rate swaps	Interest expense	$	1,844		$	1,853		$	5,460		$	5,518
	Commodity contracts	Revenue	168			(1,838		)	(896		)	(7,741		)
			2,012			15			4,564			(2,223		)
	Income tax	Income tax benefit (expense)	(586		)	13			(1,469		)	890
	Reclassification adjustments related to cash flow hedges, net of tax		$	1,426		$	28		$	3,095		$	(1,333	)
	Amortization of defined benefit plans:
	Prior service cost	Utilities - Operations and maintenance	$	(31	)	$	—		$	(93	)	$	—
		Non-regulated energy operations and maintenance	(32		)	—			(96		)	—
	Actuarial gain (loss)	Utilities - Operations and maintenance	425			—			1,267			—
		Non-regulated energy operations and maintenance	275			—			823			—
			637			—			1,901			—
	Income tax	Income tax benefit (expense)	(220		)	—			(663		)	—
	Reclassification adjustments related to defined benefit plans, net of tax		$	417		$	—		$	1,238		$	—
	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 Dec. 31, 2011	$	(13,802	)	$	(19,076	)	$	(32,878	)
	Other comprehensive income (loss), net of tax	(166		)	—			(166		)
	Balance as of March 31, 2012	(13,968		)	(19,076		)	(33,044		)
	Other comprehensive income (loss), net of tax	(608		)	—			(608		)
	Balance as of June 30, 2012	(14,576		)	(19,076		)	(33,652		)
	Other comprehensive income (loss), net of tax	(3,563		)	—			(3,563		)
	Ending Balance Sept. 30, 2012	$	(18,139	)	$	(19,076	)	$	(37,215	)
	Balance as of Dec. 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		)
	Other comprehensive income (loss), net of tax	5,079			364			5,443
	Balance as of June 30, 2013	(11,827		)	(18,954		)	(30,781		)
	Other comprehensive income (loss), net of tax	(657		)	417			(240		)
	Ending Balance Sept. 30, 2013	$	(12,484	)	$	(18,537	)	$	(31,021	)

Employee_Benefit_Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2013
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'
Employee Benefit Plans 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 Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	1,608		$	1,431		$	4,824		$	4,291
	Interest cost	3,825			3,688			11,475			11,062
	Expected return on plan assets	(4,654		)	(4,084		)	(13,962		)	(12,252		)
	Prior service cost	16			22			48			66
	Net loss (gain)	3,062			2,408			9,186			7,224
	Net periodic benefit cost	$	3,857		$	3,465		$	11,571		$	10,391
	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 Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	419		$	402		$	1,257		$	1,206
	Interest cost	417			523			1,251			1,569
	Expected return on plan assets	(20		)	(19		)	(60		)	(57		)
	Prior service cost (benefit)	(125		)	(125		)	(375		)	(375		)
	Net loss (gain)	121			222			363			666
	Net periodic benefit cost	$	812		$	1,003		$	2,436		$	3,009
	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 Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	348		$	243		$	1,044		$	735
	Interest cost	332			331			996			993
	Prior service cost	1			1			3			3
	Net loss (gain)	198			202			594			606
	Net periodic benefit cost	$	879		$	777		$	2,637		$	2,337
	Contributions
	We anticipate that we will make contributions to the benefit plans during 2013 and 2014. 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			Contributions Made			Additional
		Three Months Ended Sept. 30, 2013			Nine Months Ended Sept. 30, 2013			Contributions Anticipated for 2013			Contributions Anticipated for 2014
	Defined Benefit Pension Plans	$	12,500		$	12,500		$	—		$	12,500
	Non-pension Defined Benefit Postretirement Healthcare Plans	$	784		$	2,352		$	784		$	3,350
	Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	322		$	966		$	322		$	1,463

Business_Segment_Information

Business Segment Information	9 Months Ended
	Sep. 30, 2013
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 Sept. 30, 2013		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenue			Revenue
	Utilities:
	Electric		$	169,401		$	2,003			$	15,097
	Gas		67,792			—				(1,450		)
	Non-regulated Energy:
	Power Generation		1,575			20,393				6,707
	Coal Mining		6,713			8,604				2,142
	Oil and Gas		14,426			—				(1,682		)
	Corporate activities (a)		—			—				2,310
	Intercompany eliminations		—			(31,000		)		—
	Total		$	259,907		$	—			$	23,124
	Three Months Ended Sept. 30, 2012		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenue			Revenue
	Utilities:
	Electric		$	151,281		$	3,736			$	14,573
	Gas		63,435			—				3
	Non-regulated Energy:
	Power Generation		1,256			19,695				5,128
	Coal Mining		6,108			8,567				1,690
	Oil and Gas (b)		24,728			—				17,389
	Corporate activities (a)		—			—				(4,160		)
	Intercompany eliminations		—			(31,998		)		—
	Total		$	246,808		$	—			$	34,623
	Nine Months Ended Sept. 30, 2013		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenues			Revenues
	Utilities:
	Electric		$	482,222		$	9,844			$	38,063
	Gas		373,440			—				20,225
	Non-regulated Energy:
	Power Generation		3,628			58,825				17,382
	Coal Mining		19,530			23,688				5,180
	Oil and Gas		41,584			—				(3,699		)
	Corporate (a)		—			—				19,688
	Intercompany eliminations		—			(92,357		)		—
	Total		$	920,404		$	—			$	96,839
	Nine Months Ended Sept. 30, 2012		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenues			Revenues
	Utilities:
	Electric		$	451,974		$	11,946			$	37,478
	Gas		314,343			—				16,369
	Non-regulated Energy:
	Power Generation		3,193			56,119				15,968
	Coal Mining		18,518			24,273				3,924
	Oil and Gas (b)		66,994			—				(2,219		)
	Corporate (a)(c)		—			—				(13,949		)
	Intercompany eliminations		—			(92,338		)		—
	Total		$	855,022		$	—			$	57,571
	__________
	(a)	Income (loss) from continuing operations includes a $2.0 million and a $19.1 million net after-tax non-cash mark-to-market gain on certain interest rate swaps for the three and nine months ended Sept. 30, 2013, respectively, and a $0.4 million after-tax non-cash mark-to-market gain and a $1.9 million net after-tax non-cash mark-to-market loss for the three and nine months ended Sept. 30, 2012, respectively, for those same interest rate swaps.
	(b)	Income (loss) from continuing operations for the nine months ended Sept. 30, 2012, includes a $17.3 million non-cash after-tax ceiling test impairment charge. Income (loss) from continuing operations for the three and nine months ended Sept. 30, 2012, includes an after-tax gain of $17.7 million relating to the sale of the Williston Basin assets. See Notes 14 and 15 for further information.
	(c)	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the nine months ended Sept. 30, 2012, were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.
	Segment information and Corporate balances included in the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands):
	Total Assets (net of inter-company eliminations) as of:	Sept. 30, 2013			Dec. 31, 2012				Sept. 30, 2012
	Utilities:
	Electric (a)	$	2,464,123		$	2,387,458			$	2,302,951
	Gas	757,746			765,165				710,099
Non-regulated Energy:
Power Generation (a)	102,331			119,170				119,489
Coal Mining	82,155			83,810				90,444
Oil and Gas	264,785			258,460				263,088
Corporate activities	130,100			115,408				367,557
Total assets	$	3,801,240		$	3,729,471			$	3,853,628
__________
(a)	The PPA pertaining to the portion of the Pueblo Airport Generation Station owned by Colorado IPP that supports Colorado Electric customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total assets of Electric Utilities Segment under this accounting for a capital lease.

Risk_Management_Activities

Risk Management Activities	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Risk Managment Activities	'
	RISK MANAGEMENT ACTIVITIES
	Our activities in the regulated and non-regulated energy sectors expose us to a number of risks in the normal operation of our businesses. Depending on the activity, we are exposed to varying degrees of market risk and credit risk. To manage and mitigate these identified risks, we have adopted the Black Hills Corporation Risk Policies and Procedures as discussed in our 2012 Annual Report on Form 10-K.
	Market Risk
	Market risk is the potential loss that might occur as a result of an adverse change in market price or rate. We are exposed to the following market risks including, but not limited to:
	•	Commodity price risk associated with our natural long position 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, including our project financing floating rate debt and our other short-term and long-term debt instruments.
	Credit Risk
	Credit risk is the risk of financial loss resulting from non-performance of contractual obligations by a counterparty.
	For production and generation activities, we attempt to mitigate our credit exposure by conducting business primarily with high credit quality entities, setting tenor and credit limits commensurate with counterparty financial strength, obtaining master netting agreements, and mitigating credit exposure with less creditworthy counterparties through parental guarantees, prepayments, letters of credit, and other security agreements.
	We perform ongoing credit evaluations of our customers and adjust credit limits based upon payment history and the customer’s current creditworthiness, as determined by review of their current credit information. We maintain a provision for estimated credit losses based upon historical experience and any specific customer collection issue that is identified.
	As of Sept. 30, 2013, our credit exposure included a $1.3 million exposure to a non-investment grade energy marketing company. The remainder of our credit exposure was concentrated primarily among retail utility customers, investment grade 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 11.
	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 Sheet were as follows (dollars in thousands) as of:
		Sept. 30, 2013							Dec. 31, 2012							Sept. 30, 2012
		Crude oil futures, swaps and options			Natural gas futures and swaps				Crude oil futures, swaps and options			Natural gas futures and swaps				Crude oil futures, swaps and options			Natural gas futures and swaps
	Notional (a)	499,500			9,874,000				528,000			8,215,500				537,000			7,455,250
	Maximum terms in years (b)	0.25			0.08				1			0.75				1			1
	Derivative assets, current	$	13		$	113			$	1,405		$	1,831			$	1,651		$	2,032
	Derivative assets, non-current	$	—		$	—			$	297		$	170			$	494		$	39
	Derivative liabilities, current	$	98		$	52			$	847		$	507			$	527		$	1,040
	Derivative liabilities, non-current	$	—		$	—			$	—		$	—			$	414		$	141
	__________
	(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 Sept. 30, 2013, a $0.1 million gain would be reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market prices fluctuate.
	Utilities
	The operations of our utilities, including power purchase arrangements where our 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:
		Sept. 30, 2013					Dec. 31, 2012					Sept. 30, 2012
		Notional			Maximum		Notional			Maximum		Notional			Maximum
		(MMBtus)			Term		(MMBtus)			Term		(MMBtus)			Term
					(months)					(months)					(months)
	Natural gas futures purchased	14,010,000			74		15,350,000			83		14,690,000			75
	Natural gas options purchased	6,810,000			6		2,430,000			2		5,560,000			6
	Natural gas basis swaps purchased	9,790,000			63		12,020,000			72		8,800,000			75
	We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheet as of (in thousands):
		Sept. 30, 2013			Dec. 31, 2012			Sept. 30, 2012
	Derivative assets, current	$	—		$	—		$	12,380
	Derivative assets, non-current	$	—		$	43		$	634
	Derivative liabilities, non-current	$	—		$	—		$	4,527
	Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	10,652		$	9,596		$	9,318
	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 Sheet were as follows (dollars in thousands) as of:
		Sept. 30, 2013							Dec. 31, 2012							Sept. 30, 2012
		Designated			De-designated				Designated			De-designated				Designated			De-designated
		Interest Rate			Interest Rate				Interest Rate			Interest Rate				Interest Rate			Interest Rate
		Swaps (a)			Swaps (b)				Swaps (a)			Swaps (b)				Swaps (a)			Swaps (b)
	Notional	$	150,000		$	250,000			$	150,000		$	250,000			$	150,000		$	250,000
	Weighted average fixed interest rate	5.04		%	5.67		%		5.04		%	5.67		%		5.04		%	5.67		%
	Maximum terms in years	3.25			0.25				4			1				4.25			1.25
	Derivative liabilities, current	$	7,039		$	58,755			$	7,039		$	88,148			$	7,028		$	77,914
	Derivative liabilities, non-current	$	11,388		$	—			$	16,941		$	—			$	18,660		$	17,668
	__________
	(a)	These swaps have been designated to $75.0 million of borrowings on our Revolving Credit Facility and $75.0 million of borrowings on our project financing debt at Black Hills Wyoming. The swaps that hedge the variable rate debt at Black Hills Wyoming were transferred from BHC. Both BHC and Black Hills Wyoming are jointly and severally obligated for the swaps’ obligations. These swaps are priced using three-month LIBOR, matching the floating portion of the related swaps.
	(b)	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in approximately 5.25 years and de-designated swaps totaling $150.0 million notional terminate in approximately 15.25 years.
	Collateral requirements based on our corporate credit rating apply to $50.0 million of our de-designated swaps. At our current credit ratings, we are required to post collateral for any amount by which the swaps’ negative mark-to-market fair value exceeds $20.0 million. If our senior unsecured credit rating drops to BB+ or below by S&P, or to Ba1 or below by Moody’s, we would be required to post collateral for the entire amount of the swaps’ negative mark-to-market fair value. We had approximately $6.0 million cash collateral posted at Sept. 30, 2013.
	Based on Sept. 30, 2013, market interest rates and balances related to our designated interest rate swaps, a loss of approximately $7.0 million would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market interest rates change.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
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, 3 and 4 to the Consolidated Financial Statements included in our 2012 Annual Report on Form 10-K filed with the SEC.
	Transfers into Level 3, if any, occur when significant inputs used to value the derivative instruments become less observable such as a significant decrease in the frequency and volume in which the instrument is traded, negatively impacting the availability of observable pricing inputs. Transfers out of Level 3, if any, occur when the significant inputs become more observable, such as 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 using the instrument’s current forward price strip hedged for the same quantity and date and discounted based on the three-month LIBOR. We utilize observable inputs which support Level 2 disclosure.
	Utilities 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 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 12:
		As of Sept. 30, 2013
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	2		$	—			$	—		$	2
	Basis Swaps -- Oil	—			51			—				(40		)	11
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,752			—				(1,639		)	113
	Commodity derivatives — Utilities	—			2,351			—				(2,351		)	—
	Total	$	13,637		$	4,156		$	—			$	(4,030	)	$	126
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	142		$	—			$	(77	)	$	65
	Basis Swaps -- Oil	—			1,318			—				(1,284		)	34
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			232			—				(181		)	51
	Commodity derivatives — Utilities	—			10,747			—				(10,747		)	—
	Interest rate swaps	—			83,142			—				(5,960		)	77,182
	Total	$	—		$	95,581		$	—			$	(18,249	)	$	77,332
		As of Dec. 31, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	378		$	—			$	—		$	378
	Basis Swaps -- Oil	—			1,325			—				—			1,325
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			2,000			—				—			2,000
	Commodity derivatives —Utilities	—			—			43			(a)	—			43
	Total	$	—		$	3,703		$	43			$	—		$	3,746
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	1,131		$	—			$	(336	)	$	795
	Basis Swaps -- Oil	—			502			—				(450		)	52
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,127			—				(620		)	507
	Commodity derivatives — Utilities	—			10,162			—				(10,162		)	—
	Interest rate swaps	—			118,088			—				(5,960		)	112,128
	Total	$	—		$	131,010		$	—			$	(17,528	)	$	113,482
	__________
	(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
		As of Sept. 30, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—		$	619		$	—			$	—		$	619
Basis Swaps -- Oil	—			1,526			—				—			1,526
Options -- Gas	—			—			—				—			—
Basis Swaps -- Gas	—			2,071			—				—			2,071
Commodity derivatives — Utilities	—			(2,760		)	34			(a)	15,740			13,014
Total	$	—		$	1,456		$	34			$	15,740		$	17,230
Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—		$	885		$	—			$	—		$	885
Basis Swaps -- Oil	—			56			—				—			56
Options -- Gas	—			—			—				—			—
Basis Swaps -- Gas	—			1,181			—				—			1,181
Commodity derivatives — Utilities	—			4,527			—				—			4,527
Interest rate swaps	—			124,580			—				(3,310		)	121,270
Total	$	—		$	131,229		$	—			$	(3,310	)	$	127,919
__________
(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
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 Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the balances are not indicative of either our actual credit exposure or net economic exposure. Additionally, the amounts below will not agree with the amounts presented on our Condensed Consolidated Balance Sheets, nor will they correspond to the fair value measurements presented in Note 10.
The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands):
As of Sept. 30, 2013
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	846		$	—
Commodity derivatives	Derivative assets — non-current		959			—
Commodity derivatives	Derivative liabilities — current		—			1,317
Commodity derivatives	Derivative liabilities — non-current		—			375
Interest rate swaps	Derivative liabilities — current		—			7,039
Interest rate swaps	Derivative liabilities — non-current		—			11,388
Total derivatives designated as hedges			$	1,805		$	20,119
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	—		$	—
Commodity derivatives	Derivative assets — non-current		—			—
Commodity derivatives	Derivative liabilities — current		—			1,795
Commodity derivatives	Derivative liabilities — non-current		—			6,601
Interest rate swaps	Derivative liabilities — current		—			64,715
Interest rate swaps	Derivative liabilities — non-current		—			—
Total derivatives not designated as hedges			$	—		$	73,111
As of Dec. 31, 2012
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	2,874		$	—
Commodity derivatives	Derivative assets — non-current		510			—
Commodity derivatives	Derivative liabilities — current		—			1,993
Commodity derivatives	Derivative liabilities — non-current		—			821
Interest rate swaps	Derivative liabilities — current		—			7,038
Interest rate swaps	Derivative liabilities — non-current		—			16,941
Total derivatives designated as hedges			$	3,384		$	26,793
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	362		$	—
Commodity derivatives	Derivative assets — non-current		—			—
Commodity derivatives	Derivative liabilities — current		1,180			4,957
Commodity derivatives	Derivative liabilities — non-current		406			5,153
Interest rate swaps	Derivative liabilities — current		—			94,108
Interest rate swaps	Derivative liabilities — non-current		—			—
Total derivatives not designated as hedges			$	1,948		$	104,218
As of Sept. 30, 2012
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	3,263		$	—
Commodity derivatives	Derivative assets — non-current		533			—
Commodity derivatives	Derivative liabilities — current		—			1,534
Commodity derivatives	Derivative liabilities — non-current		—			555
Interest rate swaps	Derivative liabilities — current		—			7,029
Interest rate swaps	Derivative liabilities — non-current		—			18,661
Total derivatives designated as hedges			$	3,796		$	27,779
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	421		$	3,361
Commodity derivatives	Derivative assets — non-current		—			(634		)
Commodity derivatives	Derivative liabilities — current		—			33
Commodity derivatives	Derivative liabilities — non-current		—			4,527
Interest rate swaps	Derivative liabilities — current		—			77,913
Interest rate swaps	Derivative liabilities — non-current		—			20,977
Total derivatives not designated as hedges			$	421		$	106,177
Derivatives Offsetting
It is our policy to offset in our Condensed Consolidated Balance Sheets contracts which provide for legally enforceable netting of our accounts receivable and payable and derivative activities.
As required by accounting standards for derivatives and hedges, fair values within the following tables reconcile the gross amounts to the net amounts. Amounts included in Gross Amounts Offset on Condensed Consolidated Balance Sheets in the following tables includes the netting of asset and liability positions permitted in accordance with accounting standards for offsetting as well as the impact of legally enforceable master netting agreements that allow us to settle positive and negative positions as well as cash collateral posted with the same counterparties. Additionally, the amounts reflect cash collateral on deposit in margin accounts at Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the gross amounts are not indicative of either our actual credit exposure or net economic exposure.
Offsetting of derivative assets and derivative liabilities on our Condensed Consolidated Balance Sheets was as follows:
	As of Sept. 30, 2013
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	40		$	(40	)	$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	1,639			(1,639		)	—
Utilities	2,351			(2,351		)	—
Total derivative assets subject to a master netting agreement or similar arrangement	4,030			(4,030		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	11			—			11
Oil and Gas - Crude Options	2			—			2
Oil and Gas - Natural Gas Basis Swaps	113			—			113
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	126			—			126
Total derivative assets	$	4,156		$	(4,030	)	$	126
	As of Sept. 30, 2013
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	1,284		$	(1,284	)	$	—
Oil and Gas - Crude Options	77			(77		)	—
Oil and Gas - Natural Gas Basis Swaps	181			(181		)	—
Utilities	10,747			(10,747		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	12,289			(12,289		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	34			—			34
Oil and Gas - Crude Options	65			—			65
Oil and Gas - Natural Gas Basis Swaps	51			—			51
Utilities	—			—			—
Interest Rate Swaps	83,142			(5,960		)	77,182
Total derivative liabilities not subject to a master netting agreement or similar arrangement	83,292			(5,960		)	77,332
Total derivative liabilities	$	95,581		$	(18,249	)	$	77,332
	As of Dec. 31, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	76		$	—		$	76
Oil and Gas - Crude Options	93			—			93
Oil and Gas - Natural Gas Basis Swaps	172			—			172
Utilities	1,629			(1,586		)	43
Total derivative assets subject to a master netting agreement or similar arrangement	1,970			(1,586		)	384
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,249			—			1,249
Oil and Gas - Crude Options	285			—			285
Oil and Gas - Natural Gas Basis Swaps	1,828			—			1,828
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,362			—			3,362
Total derivative assets	$	5,332		$	(1,586	)	$	3,746
	As of Dec. 31, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	449		$	(449	)	$	—
Oil and Gas - Crude Options	337			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620			(620		)	—
Utilities	10,162			(10,162		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568			(11,568		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52			—			52
Oil and Gas - Crude Options	795			—			795
Oil and Gas - Natural Gas Basis Swaps	507			—			507
Utilities	—			—			—
Interest Rate Swaps	118,088			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442			(5,960		)	113,482
Total derivative liabilities	$	131,010		$	(17,528	)	$	113,482
	As of Sept. 30, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	95		$	—		$	95
Oil and Gas - Crude Options	194			—			194
Oil and Gas - Natural Gas Basis Swaps	5			—			5
Utilities	(2,726		)	15,740			13,014
Total derivative assets subject to a master netting agreement or similar arrangement	(2,432		)	15,740			13,308
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,431			—			1,431
Oil and Gas - Crude Options	425			—			425
Oil and Gas - Natural Gas Basis Swaps	2,066			—			2,066
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,922			—			3,922
Total derivative assets	$	1,490		$	15,740		$	17,230
	As of Sept. 30, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—		$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	—			—			—
Utilities	4,527			—			4,527
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	4,527			—			4,527
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	56			—			56
Oil and Gas - Crude Options	885			—			885
Oil and Gas - Natural Gas Basis Swaps	1,181			—			1,181
Utilities	—			—			—
Interest Rate Swaps	124,580			(3,310		)	121,270
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,702			(3,310		)	123,392
Total derivative liabilities	$	131,229		$	(3,310	)	$	127,919
Derivative assets and derivative liabilities and collateral held by counterparty included in our Condensed Consolidated Balance Sheets were (in thousands):
		As of Sept. 30, 2013
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	126			—			126
Utilities	Counterparty A	—			—			—
		$	126		$	—		$	126
		As of Sept. 30, 2013
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	(355	)	$	(355	)
Oil and Gas	Counterparty B	150			—			150
Utilities	Counterparty A	—			(3,333		)	(3,333		)
Interest Rate Swap	Counterparty D	3,563			—			3,563
Interest Rate Swap	Counterparty E	19,993			—			19,993
Interest Rate Swap	Counterparty F	9,858			—			9,858
Interest Rate Swap	Counterparty G	20,138			—			20,138
Interest Rate Swap	Counterparty H	8,857			—			8,857
Interest Rate Swap	Counterparty I	14,773			—			14,773
		$	77,332		$	(3,688	)	$	73,644
		As of Dec. 31, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	341		$	—		$	341
Oil and Gas	Counterparty B	3,362			—			3,362
Utilities	Counterparty A	43			—			43
		$	3,746		$	—		$	3,746
		As of Dec. 31, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—		$	(1,787	)	$	(1,787	)
Oil and Gas	Counterparty B	1,354			—			1,354
Utilities	Counterparty A	—			(4,354		)	(4,354		)
Interest Rate Swap	Counterparty D	4,588			—			4,588
Interest Rate Swap	Counterparty E	29,245			—			29,245
Interest Rate Swap	Counterparty F	12,721			—			12,721
Interest Rate Swap	Counterparty G	26,520			—			26,520
Interest Rate Swap	Counterparty H	16,809			—			16,809
Interest Rate Swap	Counterparty I	22,245			—			22,245
		$	113,482		$	(6,141	)	$	107,341
		As of Sept. 30, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	294		$	(2,414	)	$	(2,120	)
Oil and Gas	Counterparty B	3,922			—			3,922
Utilities	Counterparty A	13,014			—			13,014
		$	17,230		$	(2,414	)	$	14,816
		As of Sept. 30, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	2,122			—			2,122
Utilities	Counterparty A	4,527			—			4,527
Interest Rate Swap	Counterparty D	4,903			—			4,903
Interest Rate Swap	Counterparty E	31,147			—			31,147
Interest Rate Swap	Counterparty F	13,554			—			13,554
Interest Rate Swap	Counterparty G	27,610			—			27,610
Interest Rate Swap	Counterparty H	20,331			—			20,331
Interest Rate Swap	Counterparty I	23,725			—			23,725
		$	127,919		$	—		$	127,919
A description of our derivative activities is included in Note 10. The following tables present the impact that derivatives had on our Condensed Consolidated Statements of Income (Loss).
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 Sept. 30, 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		$	(907	)		Interest expense		$	(1,844	)				$	—
Commodity derivatives		(2,140		)		Revenue		(168		)				—
Total		$	(3,047	)				$	(2,012	)				$	—
Three Months Ended Sept. 30, 2012
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		$	(1,684	)		Interest expense		$	(1,853	)				$	—
Commodity derivatives		(3,111		)		Revenue		1,838						—
Total		$	(4,795	)				$	(15	)				$	—
Nine Months Ended Sept. 30, 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		$	141			Interest expense		$	(5,460	)				$	—
Commodity derivatives		86				Revenue		896						—
Total		$	227					$	(4,564	)				$	—
Nine Months Ended Sept. 30, 2012
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		$	(4,697	)		Interest expense		$	(5,518	)				$	—
Commodity derivatives		601				Revenue		7,741						—
Total		$	(4,096	)				$	2,223					$	—
Derivatives Not Designated as Hedge Instruments
The impacts of derivative instruments not designated as hedge instruments on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):
				Three Months Ended				Nine Months Ended
				Sept. 30, 2013				Sept. 30, 2013
Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
		Recognized in Income		Recognized in Income				Recognized in Income
Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	3,144			$	29,393
Interest rate swaps - realized		Interest expense		(3,300		)		(10,056		)
				$	(156	)		$	19,337
				Three Months Ended				Nine Months Ended
				Sept. 30, 2012				Sept. 30, 2012
Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
		Recognized in Income		Recognized in Income				Recognized in Income
Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	605			$	(2,902	)
Interest rate swaps - realized		Interest expense		(3,250		)		(9,697		)
Commodity derivatives		Revenue		(14		)		(14		)
				$	(2,659	)		$	(12,613	)
Other Information
On Jan. 1, 2013, we adopted ASU No. 2011-11, Disclosures about Offsetting Assets and Liabilities, which enhances disclosures by requiring an entity to disclose information about netting arrangements, including rights of offset, to enable users of its financial statements to understand the effect of those arrangements on its financial position. This ASU was effective for annual and interim reporting periods beginning on or after Jan. 1, 2013 and is to be applied retrospectively for all comparative periods presented. The impact of retrospectively adjusting for the adoption of this ASU was immaterial to our historical consolidated financial statements.
The following presents the unaudited retrospective application of ASU 2011-11 by providing reconciliation between the gross assets and gross liabilities reflected on the Consolidated Balance Sheet and the potential effects of master netting arrangements on the fair value of our derivative contracts at Dec. 31, 2011.
Offsetting of derivative assets and derivative liabilities on our Consolidated Balance Sheet was as follows (in thousands):
	As of Dec. 31, 2011
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Assets on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	965		$	8,931		$	9,896
Total derivative assets subject to a master netting agreement or similar arrangement	965			8,931			9,896
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,500			—			1,500
Oil and Gas - Natural Gas Basis Swaps	9,158			—			9,158
Total derivative assets not subject to a master netting agreement or similar arrangement	10,658			—			10,658
Total derivative assets	$	11,623		$	8,931		$	20,554
	As of Dec. 31, 2011
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Liabilities on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	17,643		$	(10,487	)	$	7,156
Total derivative liabilities subject to a master netting agreement or similar arrangement	17,643			(10,487		)	7,156
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Options	3,370			—			3,370
Oil and Gas - Natural Gas Basis Swaps	7			—			7
Interest Rate Swaps	122,867			—			122,867
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,244			—			126,244
Total derivative liabilities	$	143,887		$	(10,487	)	$	133,400
Derivative assets and derivative liabilities and collateral held by counterparty on our Consolidated Balance Sheet were (in thousands):
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	10,658			—			10,658
Utilities	Counterparty A	9,896			—			9,896
		$	20,554		$	—		$	20,554
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	3,377			—			3,377
Utilities	Counterparty A	7,156			—			7,156
Interest Rate Swap	Counterparty D	5,140			—			5,140
Interest Rate Swap	Counterparty E	31,095			—			31,095
Interest Rate Swap	Counterparty F	13,880			—			13,880
Interest Rate Swap	Counterparty G	26,329			—			26,329
Interest Rate Swap	Counterparty H	23,203			—			23,203
Interest Rate Swap	Counterparty I	23,220			—			23,220
		$	133,400		$	—		$	133,400

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2013
Fair Value of Financial Instruments [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 11, were as follows (in thousands) as of:
		Sept. 30, 2013				Dec. 31, 2012				Sept. 30, 2012
		Carrying		Fair Value		Carrying		Fair Value		Carrying		Fair Value
		Amount				Amount				Amount
	Cash and cash equivalents (a)	$	13,637	$	13,637	$	15,462	$	15,462	$	247,192	$	247,192
	Restricted cash and equivalents (a)	$	6,782	$	6,782	$	7,916	$	7,916	$	7,302	$	7,302
	Notes receivable included in Other current assets(a)	$	—	$	—	$	—	$	—	$	21,832	$	21,832
	Notes payable (a)	$	138,300	$	138,300	$	277,000	$	277,000	$	225,000	$	225,000
	Long-term debt, including current maturities (b)	$	1,211,673	$	1,325,729	$	1,042,850	$	1,231,559	$	1,271,260	$	1,471,932
	__________
	(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.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies Disclosure [Text Block]	'
	COMMITMENTS AND CONTINGENCIES
	Commitments and Contingencies
	There have been no significant changes to commitments and contingencies from those previously disclosed in Note 19 of our Notes to the Consolidated Financial Statements in our 2012 Annual Report on Form 10-K except for those described below.
	The following purchase power and power sales agreements were renewed during 2013:
	•	Cheyenne Light renewed and received FERC approval for an agreement with Basin Electric whereby Cheyenne Light will receive 40 megawatts of capacity and energy from Basin Electric through Sept. 30, 2014.
	•	Cheyenne Light renewed and received FERC approval for an agreement with Basin Electric whereby Cheyenne Light will provide 40 megawatts of capacity and energy to Basin Electric through Sept. 30, 2014.
	Purchase and Sale Agreement
	On May 6, 2013, Black Hills Wyoming entered into an agreement to sell its 40 megawatt CTII natural gas-fired generating unit to the City of Gillette, Wyo. for approximately $22 million, subject to closing adjustments. The sale is expected to close in August 2014 upon the expiration of an existing power sales agreement with Cheyenne Light under which Black Hills Wyoming sells the output of the CTII to Cheyenne Light. The sale is subject to FERC approval and certain other requirements included in the contract.
	Other Commitments
	Construction of Cheyenne Prairie, a 132 megawatt 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 Sept. 30, 2014. As of Sept. 30, 2013, committed contracts for equipment purchases and for construction were 94 percent and 67 percent complete, respectively.
	Oil Creek Fire
	On June 29, 2012, a forest and grassland fire occurred in the western Black Hills. Black Hills Power subsequently received written damage claims from the State of Wyoming and one landowner seeking recovery for alleged injury to timber, grass, fencing, fire suppression and rehabilitation costs of approximately $8 million. On April 16, 2013, thirty-four private landowners filed suit in United States District Court for the District of Wyoming, asserting similar claims, based upon allegations of negligence, common law nuisance and trespass. The suit seeks recovery of both actual and punitive damages in an unspecified amount. Our investigation into the cause and origin of the fire is pending. We expect to deny and will vigorously defend all claims arising out of the lawsuit, pending the completion of our investigation. Given the uncertainty of litigation, however, a loss related to the fire and the litigation is reasonably possible. We cannot reasonably estimate the amount of a potential loss because our investigation is ongoing. Further claims may be presented by other parties. We cannot predict the outcome of our investigation, the viability of alleged claims or the outcome of the litigation. Based on information currently available, however, management does not expect the claims, if determined adversely to us, to have a material adverse effect on our financial condition or results of operations.
	Sale of Enserco Energy Inc.
	After the sale of Enserco, our Energy Marketing segment, on Feb. 29, 2012, and pursuant to the provisions of the Stock Purchase Agreement, the buyer requested purchase price adjustments, which we disputed. The buyer filed a petition in the Colorado District Court for the City and County of Denver, Colo., seeking an order compelling binding arbitration on all of the disputed claims. Following a hearing in July 2013, the court entered an order remanding all but one of the disputed adjustment claims to arbitration. We continue to dispute the validity of the adjustment claims within the arbitration process, which we expect will conclude before the end of 2013.
	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 Sept. 30, 2013, we were in compliance with these covenants.
	Due to our holding company structure, substantially all of our operating cash flows are provided by dividends paid or distributions made by our subsidiaries. The cash to pay dividends to our stockholders is derived from these cash flows. As a result, certain statutory limitations or regulatory or financing agreements could affect the levels of distributions allowed to be made by our subsidiaries. The following restrictions on distributions from our subsidiaries existed at Sept. 30, 2013:
	•	Our utilities are generally limited to the amount of dividends allowed to be paid to us as a utility holding company under the Federal Power Act and settlement agreements with state regulatory jurisdictions. As of Sept. 30, 2013, the restricted net assets at our Utilities Group were approximately $148.6 million.
	•	As required by a covenant in the Black Hills Wyoming project financing, Black Hills Non-regulated Holdings has maintained restricted shareholders’ equity of at least $100 million.
	Guarantees
	As of Dec. 31, 2012, the Company had provided a guarantee for up to $33.3 million for Colorado Electric’s performance and payment obligations relating to the purchase of wind turbines for the Colorado Electric Busch Ranch project completed in 2012. The guarantee expired March 29, 2013, upon fulfillment of all contractual obligations.
	A guarantee of $7.5 million to Cross Timbers Energy Services for the performance and payment obligation of Black Hills Utility Holdings for natural gas supply purchases expired on June 30, 2013, and was converted to a letter of credit for $5 million as a replacement to this guarantee.

Sale_of_Assets_Notes

Sale of Assets (Notes)	9 Months Ended
	Sep. 30, 2013
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	'
	SALE OF ASSETS
	Oil and Gas
	On Sept. 27, 2012, our Oil and Gas segment sold a majority of its Bakken and Three Forks shale assets in the Williston Basin of North Dakota. An effective date of July 1, 2012, was used to determine the sales price.
	Our Oil and Gas segment follows the full-cost method of accounting for oil and gas activities. Typically, this methodology does not allow for gain or loss on sale and proceeds from sale are credited against the full cost pool. Gain or loss recognition is allowed when such adjustments would significantly alter the relationship between capitalized costs and proved reserves of oil and gas attributable to a cost center. The Williston Basin asset sale significantly altered the relationship and accordingly we recorded a gain of $27.3 million with the remainder of the proceeds recorded as a reduction in the full cost pool. This reduction in the full cost pool temporarily decreased the depreciation, depletion and amortization rate.
	Net cash proceeds, subsequent to the true-up of all post-closing adjustments, were as follows (in thousands):
	Cash proceeds received on date of sale	$	243,314
	Adjustments to proceeds:
	Final post close adjustments	2,793
	Transaction adviser fees	(1,400		)
	Payment for contractual obligation related to "back-in" fee *	(16,847		)
	Final net cash proceeds	$	227,860
	_____________
	*	Required payment, triggered by the sale of the property, arising from a contractual obligation contained in the original participation agreement with the property operator.
	Electric Utilities
	On Sept. 18, 2012, Colorado Electric completed the sale of an undivided 50 percent ownership interest in the 29 megawatt Busch Ranch Wind project to AltaGas for $25 million. Colorado Electric retains the remaining undivided interest and is the operator of this jointly owned facility. Commercial operation of the newly constructed wind farm was achieved on Oct. 16, 2012.

Impairment_of_Longlived_Assets

Impairment of Long-lived Assets (Notes)	9 Months Ended
	Sep. 30, 2013
Asset Impairment Charges [Abstract]	'
Impairment of Long-Lived Assets [Text Block]	'
	IMPAIRMENT OF LONG-LIVED ASSETS
	Under the full cost method of accounting used by our Oil and Gas segment to account for exploration, development, and acquisition of crude oil and natural gas reserves, all costs attributable to these activities are capitalized. These capitalized costs, less accumulated amortization and related deferred income taxes, are subject to a ceiling test that limits the pooled costs to the aggregate of the discounted value of future net revenue attributable to proved natural gas and crude oil reserves using a discount rate defined by the SEC plus the lower of cost or market value of unevaluated properties. Any costs in excess of the ceiling are written off as a non-cash charge.
	As a result of continued low commodity prices during the second quarter of 2012, we recorded a $26.9 million non-cash impairment of oil and gas assets included in our Oil and Gas segment as of Sept. 30, 2012. In determining the ceiling value of our assets, we utilized the average of the quoted prices from the first day of each month from the previous 12 months. For natural gas, the average NYMEX price was $3.15 per Mcf, adjusted to $2.66 per Mcf at the wellhead; for crude oil, the average NYMEX price was $95.67 per barrel, adjusted to $85.36 per barrel at the wellhead.

Part_II_Item_5_Fair_Value_Meas

Part II, Item 5 - Fair Value Measurements Fair Value Measurements (Notes)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Derivatives and Fair Value [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, 3 and 4 to the Consolidated Financial Statements included in our 2012 Annual Report on Form 10-K filed with the SEC.
	Transfers into Level 3, if any, occur when significant inputs used to value the derivative instruments become less observable such as a significant decrease in the frequency and volume in which the instrument is traded, negatively impacting the availability of observable pricing inputs. Transfers out of Level 3, if any, occur when the significant inputs become more observable, such as 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 using the instrument’s current forward price strip hedged for the same quantity and date and discounted based on the three-month LIBOR. We utilize observable inputs which support Level 2 disclosure.
	Utilities 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 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 12:
		As of Sept. 30, 2013
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	2		$	—			$	—		$	2
	Basis Swaps -- Oil	—			51			—				(40		)	11
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,752			—				(1,639		)	113
	Commodity derivatives — Utilities	—			2,351			—				(2,351		)	—
	Total	$	13,637		$	4,156		$	—			$	(4,030	)	$	126
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	142		$	—			$	(77	)	$	65
	Basis Swaps -- Oil	—			1,318			—				(1,284		)	34
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			232			—				(181		)	51
	Commodity derivatives — Utilities	—			10,747			—				(10,747		)	—
	Interest rate swaps	—			83,142			—				(5,960		)	77,182
	Total	$	—		$	95,581		$	—			$	(18,249	)	$	77,332
		As of Dec. 31, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	378		$	—			$	—		$	378
	Basis Swaps -- Oil	—			1,325			—				—			1,325
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			2,000			—				—			2,000
	Commodity derivatives —Utilities	—			—			43			(a)	—			43
	Total	$	—		$	3,703		$	43			$	—		$	3,746
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	1,131		$	—			$	(336	)	$	795
	Basis Swaps -- Oil	—			502			—				(450		)	52
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,127			—				(620		)	507
	Commodity derivatives — Utilities	—			10,162			—				(10,162		)	—
	Interest rate swaps	—			118,088			—				(5,960		)	112,128
	Total	$	—		$	131,010		$	—			$	(17,528	)	$	113,482
	__________
	(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
		As of Sept. 30, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
Assets:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—		$	619		$	—			$	—		$	619
Basis Swaps -- Oil	—			1,526			—				—			1,526
Options -- Gas	—			—			—				—			—
Basis Swaps -- Gas	—			2,071			—				—			2,071
Commodity derivatives — Utilities	—			(2,760		)	34			(a)	15,740			13,014
Total	$	—		$	1,456		$	34			$	15,740		$	17,230
Liabilities:
Commodity derivatives — Oil and Gas
Options -- Oil	$	—		$	885		$	—			$	—		$	885
Basis Swaps -- Oil	—			56			—				—			56
Options -- Gas	—			—			—				—			—
Basis Swaps -- Gas	—			1,181			—				—			1,181
Commodity derivatives — Utilities	—			4,527			—				—			4,527
Interest rate swaps	—			124,580			—				(3,310		)	121,270
Total	$	—		$	131,229		$	—			$	(3,310	)	$	127,919
__________
(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
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 Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the balances are not indicative of either our actual credit exposure or net economic exposure. Additionally, the amounts below will not agree with the amounts presented on our Condensed Consolidated Balance Sheets, nor will they correspond to the fair value measurements presented in Note 10.
The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands):
As of Sept. 30, 2013
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	846		$	—
Commodity derivatives	Derivative assets — non-current		959			—
Commodity derivatives	Derivative liabilities — current		—			1,317
Commodity derivatives	Derivative liabilities — non-current		—			375
Interest rate swaps	Derivative liabilities — current		—			7,039
Interest rate swaps	Derivative liabilities — non-current		—			11,388
Total derivatives designated as hedges			$	1,805		$	20,119
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	—		$	—
Commodity derivatives	Derivative assets — non-current		—			—
Commodity derivatives	Derivative liabilities — current		—			1,795
Commodity derivatives	Derivative liabilities — non-current		—			6,601
Interest rate swaps	Derivative liabilities — current		—			64,715
Interest rate swaps	Derivative liabilities — non-current		—			—
Total derivatives not designated as hedges			$	—		$	73,111
As of Dec. 31, 2012
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	2,874		$	—
Commodity derivatives	Derivative assets — non-current		510			—
Commodity derivatives	Derivative liabilities — current		—			1,993
Commodity derivatives	Derivative liabilities — non-current		—			821
Interest rate swaps	Derivative liabilities — current		—			7,038
Interest rate swaps	Derivative liabilities — non-current		—			16,941
Total derivatives designated as hedges			$	3,384		$	26,793
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	362		$	—
Commodity derivatives	Derivative assets — non-current		—			—
Commodity derivatives	Derivative liabilities — current		1,180			4,957
Commodity derivatives	Derivative liabilities — non-current		406			5,153
Interest rate swaps	Derivative liabilities — current		—			94,108
Interest rate swaps	Derivative liabilities — non-current		—			—
Total derivatives not designated as hedges			$	1,948		$	104,218
As of Sept. 30, 2012
	Balance Sheet Location		Fair Value			Fair Value
			of Asset			of Liability
			Derivatives			Derivatives
Derivatives designated as hedges:
Commodity derivatives	Derivative assets — current		$	3,263		$	—
Commodity derivatives	Derivative assets — non-current		533			—
Commodity derivatives	Derivative liabilities — current		—			1,534
Commodity derivatives	Derivative liabilities — non-current		—			555
Interest rate swaps	Derivative liabilities — current		—			7,029
Interest rate swaps	Derivative liabilities — non-current		—			18,661
Total derivatives designated as hedges			$	3,796		$	27,779
Derivatives not designated as hedges:
Commodity derivatives	Derivative assets — current		$	421		$	3,361
Commodity derivatives	Derivative assets — non-current		—			(634		)
Commodity derivatives	Derivative liabilities — current		—			33
Commodity derivatives	Derivative liabilities — non-current		—			4,527
Interest rate swaps	Derivative liabilities — current		—			77,913
Interest rate swaps	Derivative liabilities — non-current		—			20,977
Total derivatives not designated as hedges			$	421		$	106,177
Derivatives Offsetting
It is our policy to offset in our Condensed Consolidated Balance Sheets contracts which provide for legally enforceable netting of our accounts receivable and payable and derivative activities.
As required by accounting standards for derivatives and hedges, fair values within the following tables reconcile the gross amounts to the net amounts. Amounts included in Gross Amounts Offset on Condensed Consolidated Balance Sheets in the following tables includes the netting of asset and liability positions permitted in accordance with accounting standards for offsetting as well as the impact of legally enforceable master netting agreements that allow us to settle positive and negative positions as well as cash collateral posted with the same counterparties. Additionally, the amounts reflect cash collateral on deposit in margin accounts at Sept. 30, 2013, Dec. 31, 2012, and Sept. 30, 2012, to collateralize certain financial instruments, which are included in Derivative assets and/or Derivative liabilities. Therefore, the gross amounts are not indicative of either our actual credit exposure or net economic exposure.
Offsetting of derivative assets and derivative liabilities on our Condensed Consolidated Balance Sheets was as follows:
	As of Sept. 30, 2013
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	40		$	(40	)	$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	1,639			(1,639		)	—
Utilities	2,351			(2,351		)	—
Total derivative assets subject to a master netting agreement or similar arrangement	4,030			(4,030		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	11			—			11
Oil and Gas - Crude Options	2			—			2
Oil and Gas - Natural Gas Basis Swaps	113			—			113
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	126			—			126
Total derivative assets	$	4,156		$	(4,030	)	$	126
	As of Sept. 30, 2013
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	1,284		$	(1,284	)	$	—
Oil and Gas - Crude Options	77			(77		)	—
Oil and Gas - Natural Gas Basis Swaps	181			(181		)	—
Utilities	10,747			(10,747		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	12,289			(12,289		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	34			—			34
Oil and Gas - Crude Options	65			—			65
Oil and Gas - Natural Gas Basis Swaps	51			—			51
Utilities	—			—			—
Interest Rate Swaps	83,142			(5,960		)	77,182
Total derivative liabilities not subject to a master netting agreement or similar arrangement	83,292			(5,960		)	77,332
Total derivative liabilities	$	95,581		$	(18,249	)	$	77,332
	As of Dec. 31, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	76		$	—		$	76
Oil and Gas - Crude Options	93			—			93
Oil and Gas - Natural Gas Basis Swaps	172			—			172
Utilities	1,629			(1,586		)	43
Total derivative assets subject to a master netting agreement or similar arrangement	1,970			(1,586		)	384
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,249			—			1,249
Oil and Gas - Crude Options	285			—			285
Oil and Gas - Natural Gas Basis Swaps	1,828			—			1,828
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,362			—			3,362
Total derivative assets	$	5,332		$	(1,586	)	$	3,746
	As of Dec. 31, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	449		$	(449	)	$	—
Oil and Gas - Crude Options	337			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620			(620		)	—
Utilities	10,162			(10,162		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568			(11,568		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52			—			52
Oil and Gas - Crude Options	795			—			795
Oil and Gas - Natural Gas Basis Swaps	507			—			507
Utilities	—			—			—
Interest Rate Swaps	118,088			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442			(5,960		)	113,482
Total derivative liabilities	$	131,010		$	(17,528	)	$	113,482
	As of Sept. 30, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	95		$	—		$	95
Oil and Gas - Crude Options	194			—			194
Oil and Gas - Natural Gas Basis Swaps	5			—			5
Utilities	(2,726		)	15,740			13,014
Total derivative assets subject to a master netting agreement or similar arrangement	(2,432		)	15,740			13,308
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,431			—			1,431
Oil and Gas - Crude Options	425			—			425
Oil and Gas - Natural Gas Basis Swaps	2,066			—			2,066
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,922			—			3,922
Total derivative assets	$	1,490		$	15,740		$	17,230
	As of Sept. 30, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—		$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	—			—			—
Utilities	4,527			—			4,527
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	4,527			—			4,527
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	56			—			56
Oil and Gas - Crude Options	885			—			885
Oil and Gas - Natural Gas Basis Swaps	1,181			—			1,181
Utilities	—			—			—
Interest Rate Swaps	124,580			(3,310		)	121,270
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,702			(3,310		)	123,392
Total derivative liabilities	$	131,229		$	(3,310	)	$	127,919
Derivative assets and derivative liabilities and collateral held by counterparty included in our Condensed Consolidated Balance Sheets were (in thousands):
		As of Sept. 30, 2013
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	126			—			126
Utilities	Counterparty A	—			—			—
		$	126		$	—		$	126
		As of Sept. 30, 2013
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	(355	)	$	(355	)
Oil and Gas	Counterparty B	150			—			150
Utilities	Counterparty A	—			(3,333		)	(3,333		)
Interest Rate Swap	Counterparty D	3,563			—			3,563
Interest Rate Swap	Counterparty E	19,993			—			19,993
Interest Rate Swap	Counterparty F	9,858			—			9,858
Interest Rate Swap	Counterparty G	20,138			—			20,138
Interest Rate Swap	Counterparty H	8,857			—			8,857
Interest Rate Swap	Counterparty I	14,773			—			14,773
		$	77,332		$	(3,688	)	$	73,644
		As of Dec. 31, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	341		$	—		$	341
Oil and Gas	Counterparty B	3,362			—			3,362
Utilities	Counterparty A	43			—			43
		$	3,746		$	—		$	3,746
		As of Dec. 31, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—		$	(1,787	)	$	(1,787	)
Oil and Gas	Counterparty B	1,354			—			1,354
Utilities	Counterparty A	—			(4,354		)	(4,354		)
Interest Rate Swap	Counterparty D	4,588			—			4,588
Interest Rate Swap	Counterparty E	29,245			—			29,245
Interest Rate Swap	Counterparty F	12,721			—			12,721
Interest Rate Swap	Counterparty G	26,520			—			26,520
Interest Rate Swap	Counterparty H	16,809			—			16,809
Interest Rate Swap	Counterparty I	22,245			—			22,245
		$	113,482		$	(6,141	)	$	107,341
		As of Sept. 30, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Assets:
Oil and Gas	Counterparty A	$	294		$	(2,414	)	$	(2,120	)
Oil and Gas	Counterparty B	3,922			—			3,922
Utilities	Counterparty A	13,014			—			13,014
		$	17,230		$	(2,414	)	$	14,816
		As of Sept. 30, 2012
					Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	2,122			—			2,122
Utilities	Counterparty A	4,527			—			4,527
Interest Rate Swap	Counterparty D	4,903			—			4,903
Interest Rate Swap	Counterparty E	31,147			—			31,147
Interest Rate Swap	Counterparty F	13,554			—			13,554
Interest Rate Swap	Counterparty G	27,610			—			27,610
Interest Rate Swap	Counterparty H	20,331			—			20,331
Interest Rate Swap	Counterparty I	23,725			—			23,725
		$	127,919		$	—		$	127,919
A description of our derivative activities is included in Note 10. The following tables present the impact that derivatives had on our Condensed Consolidated Statements of Income (Loss).
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 Sept. 30, 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		$	(907	)		Interest expense		$	(1,844	)				$	—
Commodity derivatives		(2,140		)		Revenue		(168		)				—
Total		$	(3,047	)				$	(2,012	)				$	—
Three Months Ended Sept. 30, 2012
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		$	(1,684	)		Interest expense		$	(1,853	)				$	—
Commodity derivatives		(3,111		)		Revenue		1,838						—
Total		$	(4,795	)				$	(15	)				$	—
Nine Months Ended Sept. 30, 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		$	141			Interest expense		$	(5,460	)				$	—
Commodity derivatives		86				Revenue		896						—
Total		$	227					$	(4,564	)				$	—
Nine Months Ended Sept. 30, 2012
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		$	(4,697	)		Interest expense		$	(5,518	)				$	—
Commodity derivatives		601				Revenue		7,741						—
Total		$	(4,096	)				$	2,223					$	—
Derivatives Not Designated as Hedge Instruments
The impacts of derivative instruments not designated as hedge instruments on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):
				Three Months Ended				Nine Months Ended
				Sept. 30, 2013				Sept. 30, 2013
Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
		Recognized in Income		Recognized in Income				Recognized in Income
Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	3,144			$	29,393
Interest rate swaps - realized		Interest expense		(3,300		)		(10,056		)
				$	(156	)		$	19,337
				Three Months Ended				Nine Months Ended
				Sept. 30, 2012				Sept. 30, 2012
Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
		Recognized in Income		Recognized in Income				Recognized in Income
Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	605			$	(2,902	)
Interest rate swaps - realized		Interest expense		(3,250		)		(9,697		)
Commodity derivatives		Revenue		(14		)		(14		)
				$	(2,659	)		$	(12,613	)
Other Information
On Jan. 1, 2013, we adopted ASU No. 2011-11, Disclosures about Offsetting Assets and Liabilities, which enhances disclosures by requiring an entity to disclose information about netting arrangements, including rights of offset, to enable users of its financial statements to understand the effect of those arrangements on its financial position. This ASU was effective for annual and interim reporting periods beginning on or after Jan. 1, 2013 and is to be applied retrospectively for all comparative periods presented. The impact of retrospectively adjusting for the adoption of this ASU was immaterial to our historical consolidated financial statements.
The following presents the unaudited retrospective application of ASU 2011-11 by providing reconciliation between the gross assets and gross liabilities reflected on the Consolidated Balance Sheet and the potential effects of master netting arrangements on the fair value of our derivative contracts at Dec. 31, 2011.
Offsetting of derivative assets and derivative liabilities on our Consolidated Balance Sheet was as follows (in thousands):
	As of Dec. 31, 2011
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Assets on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	965		$	8,931		$	9,896
Total derivative assets subject to a master netting agreement or similar arrangement	965			8,931			9,896
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,500			—			1,500
Oil and Gas - Natural Gas Basis Swaps	9,158			—			9,158
Total derivative assets not subject to a master netting agreement or similar arrangement	10,658			—			10,658
Total derivative assets	$	11,623		$	8,931		$	20,554
	As of Dec. 31, 2011
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Liabilities on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	17,643		$	(10,487	)	$	7,156
Total derivative liabilities subject to a master netting agreement or similar arrangement	17,643			(10,487		)	7,156
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Options	3,370			—			3,370
Oil and Gas - Natural Gas Basis Swaps	7			—			7
Interest Rate Swaps	122,867			—			122,867
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,244			—			126,244
Total derivative liabilities	$	143,887		$	(10,487	)	$	133,400
Derivative assets and derivative liabilities and collateral held by counterparty on our Consolidated Balance Sheet were (in thousands):
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	10,658			—			10,658
Utilities	Counterparty A	9,896			—			9,896
		$	20,554		$	—		$	20,554
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	3,377			—			3,377
Utilities	Counterparty A	7,156			—			7,156
Interest Rate Swap	Counterparty D	5,140			—			5,140
Interest Rate Swap	Counterparty E	31,095			—			31,095
Interest Rate Swap	Counterparty F	13,880			—			13,880
Interest Rate Swap	Counterparty G	26,329			—			26,329
Interest Rate Swap	Counterparty H	23,203			—			23,203
Interest Rate Swap	Counterparty I	23,220			—			23,220
		$	133,400		$	—		$	133,400

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information Supplmental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Disclosures of Cash Flows [Table Text Block]	'
	Supplemental disclosures of cash flow for the nine months ended are as follows (in thousands):
		Nine Months Ended
		Sept. 30, 2013			Sept. 30, 2012
	Non-cash investing and financing activities from continuing operations—
	Property, plant and equipment acquired with accrued liabilities	$	47,214		$	39,303
	Increase (decrease) in capitalized assets associated with asset retirement obligations	$	—		$	3,806
	Cash (paid) refunded during the period for continuing operations—
	Interest (net of amounts capitalized)	$	(57,175	)	$	(69,901	)
	Income taxes, net	$	(4,924	)	$	425

Materials_Supplies_and_Fuel_Ma

Materials, Supplies and Fuel Materials, Supplies and Fuel (Tables)	9 Months Ended
	Sep. 30, 2013
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:
		Sept. 30, 2013		Dec. 31, 2012		Sept. 30, 2012
	Materials and supplies	$	50,564	$	43,397	$	43,847
	Fuel - Electric Utilities	6,384		8,589		8,289
	Natural gas in storage held for distribution	38,282		25,657		28,764
	Total materials, supplies and fuel	$	95,230	$	77,643	$	80,900

Accounts_Receivable_Accounts_R

Accounts Receivable Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2013
Receivables [Abstract]	'
Schedule of Accounts Receivable [Table Text Block]	'
	Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of:
		Accounts		Unbilled		Less Allowance for			Accounts
	Sept. 30, 2013	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	49,254	$	20,153	$	(648	)	$	68,759
	Gas Utilities	20,693		11,877		(542		)	32,028
	Power Generation	3		—		—			3
	Coal Mining	2,677		—		—			2,677
	Oil and Gas	8,463		—		(19		)	8,444
	Corporate	2,226		—		—			2,226
	Total	$	83,316	$	32,030	$	(1,209	)	$	114,137
		Accounts		Unbilled		Less Allowance for			Accounts
	Dec. 31, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	54,482	$	23,843	$	(527	)	$	77,798
	Gas Utilities	31,495		39,962		(222		)	71,235
	Power Generation	16		—		—			16
	Coal Mining	2,247		—		—			2,247
	Oil and Gas	11,622		—		(19		)	11,603
	Corporate	799		—		—			799
	Total	$	100,661	$	63,805	$	(768	)	$	163,698
		Accounts		Unbilled		Less Allowance for			Accounts
	Sept. 30, 2012	Receivable, Trade		Revenue		Doubtful Accounts			Receivable, net
	Electric Utilities	$	46,802	$	18,441	$	(603	)	$	64,640
	Gas Utilities	18,198		9,480		(204		)	27,474
	Power Generation	4		—		—			4
	Coal Mining	1,540		—		—			1,540
	Oil and Gas	10,272		—		(105		)	10,167
	Corporate	657		—		—			657
	Total	$	77,473	$	27,921	$	(912	)	$	104,482

Notes_Payable_and_LongTerm_Deb1

Notes Payable and Long-Term Debt Schedule Of Short Term Debt (Tables)	9 Months Ended
	Sep. 30, 2013
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:
		Sept. 30, 2013					Dec. 31, 2012				Sept. 30, 2012
		Balance Outstanding		Letters of Credit			Balance Outstanding		Letters of Credit		Balance Outstanding		Letters of Credit
	Revolving Credit Facility	$	138,300	$	53,137		$	127,000	$	36,300	$	75,000	$	36,300
	Term Loan due June 2013	—		—			150,000		—		150,000		—
	Total	$	138,300	$	53,137		$	277,000	$	36,300	$	225,000	$	36,300
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 (dollars in thousands):
		As of
		Sept. 30, 2013		Covenant Requirement
	Recourse Leverage Ratio	52	%	Less than	65	%

Earnings_Per_Share_Earnings_Pe

Earnings Per Share Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Schedule of Earnings Per Share Reconciliation [Table Text Block]	'
	A reconciliation of share amounts used to compute Earnings (loss) per share in the accompanying Condensed Consolidated Statements of Income (loss) is as follows (in thousands):
		Three Months Ended Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013		2012
	Income (loss) from continuing operations	$	23,124		$	34,623		$	96,839	$	57,571
	Weighted average shares - basic	44,201			43,847			44,143		43,792
	Dilutive effect of:
	Restricted stock	131			175			137		159
	Stock options	13			12			13		14
	Other dilutive effects	112			74			102		61
	Weighted average shares - diluted	44,457			44,108			44,395		44,026
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 Sept. 30,				Nine Months Ended Sept. 30,
		2013		2012		2013	2012
	Stock options	—		77		9	101
	Restricted stock	—		61		—	53
	Other stock	—		—		—	19
	Anti-dilutive shares	—		138		9	173

Other_Comprehensive_Income_Oth

Other Comprehensive Income Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2013
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						Nine Months Ended
			Sept. 30, 2013			Sept. 30, 2012			Sept. 30, 2013			Sept. 30, 2012
	Gains (losses) on cash flow hedges:
	Interest rate swaps	Interest expense	$	1,844		$	1,853		$	5,460		$	5,518
	Commodity contracts	Revenue	168			(1,838		)	(896		)	(7,741		)
			2,012			15			4,564			(2,223		)
	Income tax	Income tax benefit (expense)	(586		)	13			(1,469		)	890
	Reclassification adjustments related to cash flow hedges, net of tax		$	1,426		$	28		$	3,095		$	(1,333	)
	Amortization of defined benefit plans:
	Prior service cost	Utilities - Operations and maintenance	$	(31	)	$	—		$	(93	)	$	—
		Non-regulated energy operations and maintenance	(32		)	—			(96		)	—
	Actuarial gain (loss)	Utilities - Operations and maintenance	425			—			1,267			—
		Non-regulated energy operations and maintenance	275			—			823			—
			637			—			1,901			—
	Income tax	Income tax benefit (expense)	(220		)	—			(663		)	—
	Reclassification adjustments related to defined benefit plans, net of tax		$	417		$	—		$	1,238		$	—
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 Dec. 31, 2011	$	(13,802	)	$	(19,076	)	$	(32,878	)
	Other comprehensive income (loss), net of tax	(166		)	—			(166		)
	Balance as of March 31, 2012	(13,968		)	(19,076		)	(33,044		)
	Other comprehensive income (loss), net of tax	(608		)	—			(608		)
	Balance as of June 30, 2012	(14,576		)	(19,076		)	(33,652		)
	Other comprehensive income (loss), net of tax	(3,563		)	—			(3,563		)
	Ending Balance Sept. 30, 2012	$	(18,139	)	$	(19,076	)	$	(37,215	)
	Balance as of Dec. 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		)
	Other comprehensive income (loss), net of tax	5,079			364			5,443
	Balance as of June 30, 2013	(11,827		)	(18,954		)	(30,781		)
	Other comprehensive income (loss), net of tax	(657		)	417			(240		)
	Ending Balance Sept. 30, 2013	$	(12,484	)	$	(18,537	)	$	(31,021	)

Employee_Benefit_Plans_Employe

Employee Benefit Plans Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Defined Benefit Plans Contributions [Table Text Block]	'
	Contributions and anticipated contributions are as follows (in thousands):
		Contributions Made			Contributions Made			Additional
		Three Months Ended Sept. 30, 2013			Nine Months Ended Sept. 30, 2013			Contributions Anticipated for 2013			Contributions Anticipated for 2014
	Defined Benefit Pension Plans	$	12,500		$	12,500		$	—		$	12,500
	Non-pension Defined Benefit Postretirement Healthcare Plans	$	784		$	2,352		$	784		$	3,350
	Supplemental Non-qualified Defined Benefit and Defined Contribution Plans	$	322		$	966		$	322		$	1,463
Defined Benefit Pension Plan [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
	The components of net periodic benefit cost for the Defined Benefit Pension Plans were as follows (in thousands):
		Three Months Ended Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	1,608		$	1,431		$	4,824		$	4,291
	Interest cost	3,825			3,688			11,475			11,062
	Expected return on plan assets	(4,654		)	(4,084		)	(13,962		)	(12,252		)
	Prior service cost	16			22			48			66
	Net loss (gain)	3,062			2,408			9,186			7,224
	Net periodic benefit cost	$	3,857		$	3,465		$	11,571		$	10,391
Non-pension Defined Benefit Postretirement Healthcare Plans [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
	The components of net periodic benefit cost for the Non-pension Defined Benefit Postretirement Healthcare Plans were as follows (in thousands):
		Three Months Ended Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	419		$	402		$	1,257		$	1,206
	Interest cost	417			523			1,251			1,569
	Expected return on plan assets	(20		)	(19		)	(60		)	(57		)
	Prior service cost (benefit)	(125		)	(125		)	(375		)	(375		)
	Net loss (gain)	121			222			363			666
	Net periodic benefit cost	$	812		$	1,003		$	2,436		$	3,009
Supplemenatal Non-qualified Defined Benefit Plans [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
	The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit and Defined Contribution Plans were as follows (in thousands):
		Three Months Ended Sept. 30,						Nine Months Ended Sept. 30,
		2013			2012			2013			2012
	Service cost	$	348		$	243		$	1,044		$	735
	Interest cost	332			331			996			993
	Prior service cost	1			1			3			3
	Net loss (gain)	198			202			594			606
	Net periodic benefit cost	$	879		$	777		$	2,637		$	2,337

Business_Segment_Information_B

Business Segment Information Business Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
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 Sept. 30, 2013		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenue			Revenue
	Utilities:
	Electric		$	169,401		$	2,003			$	15,097
	Gas		67,792			—				(1,450		)
	Non-regulated Energy:
	Power Generation		1,575			20,393				6,707
	Coal Mining		6,713			8,604				2,142
	Oil and Gas		14,426			—				(1,682		)
	Corporate activities (a)		—			—				2,310
	Intercompany eliminations		—			(31,000		)		—
	Total		$	259,907		$	—			$	23,124
	Three Months Ended Sept. 30, 2012		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenue			Revenue
	Utilities:
	Electric		$	151,281		$	3,736			$	14,573
	Gas		63,435			—				3
	Non-regulated Energy:
	Power Generation		1,256			19,695				5,128
	Coal Mining		6,108			8,567				1,690
	Oil and Gas (b)		24,728			—				17,389
	Corporate activities (a)		—			—				(4,160		)
	Intercompany eliminations		—			(31,998		)		—
	Total		$	246,808		$	—			$	34,623
	Nine Months Ended Sept. 30, 2013		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenues			Revenues
	Utilities:
	Electric		$	482,222		$	9,844			$	38,063
	Gas		373,440			—				20,225
	Non-regulated Energy:
	Power Generation		3,628			58,825				17,382
	Coal Mining		19,530			23,688				5,180
	Oil and Gas		41,584			—				(3,699		)
	Corporate (a)		—			—				19,688
	Intercompany eliminations		—			(92,357		)		—
	Total		$	920,404		$	—			$	96,839
	Nine Months Ended Sept. 30, 2012		External			Intercompany				Income (Loss) from Continuing Operations
			Operating			Operating
			Revenues			Revenues
	Utilities:
	Electric		$	451,974		$	11,946			$	37,478
	Gas		314,343			—				16,369
	Non-regulated Energy:
	Power Generation		3,193			56,119				15,968
	Coal Mining		18,518			24,273				3,924
	Oil and Gas (b)		66,994			—				(2,219		)
	Corporate (a)(c)		—			—				(13,949		)
	Intercompany eliminations		—			(92,338		)		—
	Total		$	855,022		$	—			$	57,571
	__________
	(a)	Income (loss) from continuing operations includes a $2.0 million and a $19.1 million net after-tax non-cash mark-to-market gain on certain interest rate swaps for the three and nine months ended Sept. 30, 2013, respectively, and a $0.4 million after-tax non-cash mark-to-market gain and a $1.9 million net after-tax non-cash mark-to-market loss for the three and nine months ended Sept. 30, 2012, respectively, for those same interest rate swaps.
	(b)	Income (loss) from continuing operations for the nine months ended Sept. 30, 2012, includes a $17.3 million non-cash after-tax ceiling test impairment charge. Income (loss) from continuing operations for the three and nine months ended Sept. 30, 2012, includes an after-tax gain of $17.7 million relating to the sale of the Williston Basin assets. See Notes 14 and 15 for further information.
	(c)	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the nine months ended Sept. 30, 2012, were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.
	Segment information and Corporate balances included in the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands):
	Total Assets (net of inter-company eliminations) as of:	Sept. 30, 2013			Dec. 31, 2012				Sept. 30, 2012
	Utilities:
	Electric (a)	$	2,464,123		$	2,387,458			$	2,302,951
	Gas	757,746			765,165				710,099
	Non-regulated Energy:
Power Generation (a)	102,331			119,170				119,489
Coal Mining	82,155			83,810				90,444
Oil and Gas	264,785			258,460				263,088
Corporate activities	130,100			115,408				367,557
Total assets	$	3,801,240		$	3,729,471			$	3,853,628
__________
(a)	The PPA pertaining to the portion of the Pueblo Airport Generation Station owned by Colorado IPP that supports Colorado Electric customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total assets of Electric Utilities Segment under this accounting for a capital lease.

Risk_Management_Activities_Ris

Risk Management Activities Risk Management Activities (Tables)	9 Months Ended
	Sep. 30, 2013
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 Sheet were as follows (dollars in thousands) as of:
		Sept. 30, 2013							Dec. 31, 2012							Sept. 30, 2012
		Designated			De-designated				Designated			De-designated				Designated			De-designated
		Interest Rate			Interest Rate				Interest Rate			Interest Rate				Interest Rate			Interest Rate
		Swaps (a)			Swaps (b)				Swaps (a)			Swaps (b)				Swaps (a)			Swaps (b)
	Notional	$	150,000		$	250,000			$	150,000		$	250,000			$	150,000		$	250,000
	Weighted average fixed interest rate	5.04		%	5.67		%		5.04		%	5.67		%		5.04		%	5.67		%
	Maximum terms in years	3.25			0.25				4			1				4.25			1.25
	Derivative liabilities, current	$	7,039		$	58,755			$	7,039		$	88,148			$	7,028		$	77,914
	Derivative liabilities, non-current	$	11,388		$	—			$	16,941		$	—			$	18,660		$	17,668
	__________
	(a)	These swaps have been designated to $75.0 million of borrowings on our Revolving Credit Facility and $75.0 million of borrowings on our project financing debt at Black Hills Wyoming. The swaps that hedge the variable rate debt at Black Hills Wyoming were transferred from BHC. Both BHC and Black Hills Wyoming are jointly and severally obligated for the swaps’ obligations. These swaps are priced using three-month LIBOR, matching the floating portion of the related swaps.
	(b)	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in approximately 5.25 years and de-designated swaps totaling $150.0 million notional terminate in approximately 15.25 years.
Schedule of Derivative Instruments Balance Sheet Location [Table Text Block]	'
	The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands):
	As of Sept. 30, 2013
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	846		$	—
	Commodity derivatives	Derivative assets — non-current		959			—
	Commodity derivatives	Derivative liabilities — current		—			1,317
	Commodity derivatives	Derivative liabilities — non-current		—			375
	Interest rate swaps	Derivative liabilities — current		—			7,039
	Interest rate swaps	Derivative liabilities — non-current		—			11,388
	Total derivatives designated as hedges			$	1,805		$	20,119
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	—		$	—
	Commodity derivatives	Derivative assets — non-current		—			—
	Commodity derivatives	Derivative liabilities — current		—			1,795
	Commodity derivatives	Derivative liabilities — non-current		—			6,601
	Interest rate swaps	Derivative liabilities — current		—			64,715
	Interest rate swaps	Derivative liabilities — non-current		—			—
	Total derivatives not designated as hedges			$	—		$	73,111
	As of Dec. 31, 2012
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	2,874		$	—
	Commodity derivatives	Derivative assets — non-current		510			—
	Commodity derivatives	Derivative liabilities — current		—			1,993
	Commodity derivatives	Derivative liabilities — non-current		—			821
	Interest rate swaps	Derivative liabilities — current		—			7,038
	Interest rate swaps	Derivative liabilities — non-current		—			16,941
	Total derivatives designated as hedges			$	3,384		$	26,793
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	362		$	—
	Commodity derivatives	Derivative assets — non-current		—			—
	Commodity derivatives	Derivative liabilities — current		1,180			4,957
	Commodity derivatives	Derivative liabilities — non-current		406			5,153
	Interest rate swaps	Derivative liabilities — current		—			94,108
	Interest rate swaps	Derivative liabilities — non-current		—			—
	Total derivatives not designated as hedges			$	1,948		$	104,218
	As of Sept. 30, 2012
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	3,263		$	—
	Commodity derivatives	Derivative assets — non-current		533			—
	Commodity derivatives	Derivative liabilities — current		—			1,534
	Commodity derivatives	Derivative liabilities — non-current		—			555
	Interest rate swaps	Derivative liabilities — current		—			7,029
	Interest rate swaps	Derivative liabilities — non-current		—			18,661
	Total derivatives designated as hedges			$	3,796		$	27,779
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	421		$	3,361
	Commodity derivatives	Derivative assets — non-current		—			(634		)
	Commodity derivatives	Derivative liabilities — current		—			33
	Commodity derivatives	Derivative liabilities — non-current		—			4,527
	Interest rate swaps	Derivative liabilities — current		—			77,913
	Interest rate swaps	Derivative liabilities — non-current		—			20,977
	Total derivatives not designated as hedges			$	421		$	106,177
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 Sheet were as follows (dollars in thousands) as of:
		Sept. 30, 2013							Dec. 31, 2012							Sept. 30, 2012
		Crude oil futures, swaps and options			Natural gas futures and swaps				Crude oil futures, swaps and options			Natural gas futures and swaps				Crude oil futures, swaps and options			Natural gas futures and swaps
	Notional (a)	499,500			9,874,000				528,000			8,215,500				537,000			7,455,250
	Maximum terms in years (b)	0.25			0.08				1			0.75				1			1
	Derivative assets, current	$	13		$	113			$	1,405		$	1,831			$	1,651		$	2,032
	Derivative assets, non-current	$	—		$	—			$	297		$	170			$	494		$	39
	Derivative liabilities, current	$	98		$	52			$	847		$	507			$	527		$	1,040
	Derivative liabilities, non-current	$	—		$	—			$	—		$	—			$	414		$	141
	__________
	(a)	Crude oil in Bbls, natural gas in MMBtus.
	(b)	Refers to the term of the derivative instrument. Assets and liabilities are classified as current/non-current based on the term of the hedged transaction and the corresponding settlement of the derivative instrument.
Utilities Group [Member]	'
Derivative [Line Items]	'
Contract or Notional Amounts and Terms of Commodity Derivatives[Table Text Block]	'
	The contract or notional amounts and terms of the natural gas derivative commodity instruments held at our Utilities were as follows, as of:
		Sept. 30, 2013					Dec. 31, 2012					Sept. 30, 2012
		Notional			Maximum		Notional			Maximum		Notional			Maximum
		(MMBtus)			Term		(MMBtus)			Term		(MMBtus)			Term
					(months)					(months)					(months)
	Natural gas futures purchased	14,010,000			74		15,350,000			83		14,690,000			75
	Natural gas options purchased	6,810,000			6		2,430,000			2		5,560,000			6
	Natural gas basis swaps purchased	9,790,000			63		12,020,000			72		8,800,000			75
Schedule of Derivative Instruments Balance Sheet Location [Table Text Block]	'
	We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheet as of (in thousands):
		Sept. 30, 2013			Dec. 31, 2012			Sept. 30, 2012
	Derivative assets, current	$	—		$	—		$	12,380
	Derivative assets, non-current	$	—		$	43		$	634
	Derivative liabilities, non-current	$	—		$	—		$	4,527
	Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities	$	10,652		$	9,596		$	9,318

Fair_Value_Measurements_Fair_V

Fair Value Measurements Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]	'
Schedule of Fair Value Hierarchy, Measured on Recurring Basis [Table Text Block]	'
	The following tables set forth by level within the fair value hierarchy our 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 12:
		As of Sept. 30, 2013
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	2		$	—			$	—		$	2
	Basis Swaps -- Oil	—			51			—				(40		)	11
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,752			—				(1,639		)	113
	Commodity derivatives — Utilities	—			2,351			—				(2,351		)	—
	Total	$	13,637		$	4,156		$	—			$	(4,030	)	$	126
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	142		$	—			$	(77	)	$	65
	Basis Swaps -- Oil	—			1,318			—				(1,284		)	34
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			232			—				(181		)	51
	Commodity derivatives — Utilities	—			10,747			—				(10,747		)	—
	Interest rate swaps	—			83,142			—				(5,960		)	77,182
	Total	$	—		$	95,581		$	—			$	(18,249	)	$	77,332
		As of Dec. 31, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	378		$	—			$	—		$	378
	Basis Swaps -- Oil	—			1,325			—				—			1,325
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			2,000			—				—			2,000
	Commodity derivatives —Utilities	—			—			43			(a)	—			43
	Total	$	—		$	3,703		$	43			$	—		$	3,746
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	1,131		$	—			$	(336	)	$	795
	Basis Swaps -- Oil	—			502			—				(450		)	52
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,127			—				(620		)	507
	Commodity derivatives — Utilities	—			10,162			—				(10,162		)	—
	Interest rate swaps	—			118,088			—				(5,960		)	112,128
	Total	$	—		$	131,010		$	—			$	(17,528	)	$	113,482
	__________
	(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
		As of Sept. 30, 2012
		Level 1			Level 2			Level 3				Cash Collateral and Counterparty			Total
												Netting
		(in thousands)
	Assets:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	619		$	—			$	—		$	619
	Basis Swaps -- Oil	—			1,526			—				—			1,526
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			2,071			—				—			2,071
	Commodity derivatives — Utilities	—			(2,760		)	34			(a)	15,740			13,014
	Total	$	—		$	1,456		$	34			$	15,740		$	17,230
	Liabilities:
	Commodity derivatives — Oil and Gas
	Options -- Oil	$	—		$	885		$	—			$	—		$	885
	Basis Swaps -- Oil	—			56			—				—			56
	Options -- Gas	—			—			—				—			—
	Basis Swaps -- Gas	—			1,181			—				—			1,181
Commodity derivatives — Utilities	—			4,527			—				—			4,527
Interest rate swaps	—			124,580			—				(3,310		)	121,270
Total	$	—		$	131,229		$	—			$	(3,310	)	$	127,919
__________
(a)	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.
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 Sept. 30, 2013
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	846		$	—
	Commodity derivatives	Derivative assets — non-current		959			—
	Commodity derivatives	Derivative liabilities — current		—			1,317
	Commodity derivatives	Derivative liabilities — non-current		—			375
	Interest rate swaps	Derivative liabilities — current		—			7,039
	Interest rate swaps	Derivative liabilities — non-current		—			11,388
	Total derivatives designated as hedges			$	1,805		$	20,119
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	—		$	—
	Commodity derivatives	Derivative assets — non-current		—			—
	Commodity derivatives	Derivative liabilities — current		—			1,795
	Commodity derivatives	Derivative liabilities — non-current		—			6,601
	Interest rate swaps	Derivative liabilities — current		—			64,715
	Interest rate swaps	Derivative liabilities — non-current		—			—
	Total derivatives not designated as hedges			$	—		$	73,111
	As of Dec. 31, 2012
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	2,874		$	—
	Commodity derivatives	Derivative assets — non-current		510			—
	Commodity derivatives	Derivative liabilities — current		—			1,993
	Commodity derivatives	Derivative liabilities — non-current		—			821
	Interest rate swaps	Derivative liabilities — current		—			7,038
	Interest rate swaps	Derivative liabilities — non-current		—			16,941
	Total derivatives designated as hedges			$	3,384		$	26,793
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	362		$	—
	Commodity derivatives	Derivative assets — non-current		—			—
	Commodity derivatives	Derivative liabilities — current		1,180			4,957
	Commodity derivatives	Derivative liabilities — non-current		406			5,153
	Interest rate swaps	Derivative liabilities — current		—			94,108
	Interest rate swaps	Derivative liabilities — non-current		—			—
	Total derivatives not designated as hedges			$	1,948		$	104,218
	As of Sept. 30, 2012
		Balance Sheet Location		Fair Value			Fair Value
				of Asset			of Liability
				Derivatives			Derivatives
	Derivatives designated as hedges:
	Commodity derivatives	Derivative assets — current		$	3,263		$	—
	Commodity derivatives	Derivative assets — non-current		533			—
	Commodity derivatives	Derivative liabilities — current		—			1,534
	Commodity derivatives	Derivative liabilities — non-current		—			555
	Interest rate swaps	Derivative liabilities — current		—			7,029
	Interest rate swaps	Derivative liabilities — non-current		—			18,661
	Total derivatives designated as hedges			$	3,796		$	27,779
	Derivatives not designated as hedges:
	Commodity derivatives	Derivative assets — current		$	421		$	3,361
	Commodity derivatives	Derivative assets — non-current		—			(634		)
	Commodity derivatives	Derivative liabilities — current		—			33
	Commodity derivatives	Derivative liabilities — non-current		—			4,527
	Interest rate swaps	Derivative liabilities — current		—			77,913
	Interest rate swaps	Derivative liabilities — non-current		—			20,977
	Total derivatives not designated as hedges			$	421		$	106,177
Schedule of Derivative Offsetting On Balance Sheet [Table Text Block]	'
	Offsetting of derivative assets and derivative liabilities on our Condensed Consolidated Balance Sheets was as follows:
		As of Sept. 30, 2013
	Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	40		$	(40	)	$	—
	Oil and Gas - Crude Options	—			—			—
	Oil and Gas - Natural Gas Basis Swaps	1,639			(1,639		)	—
	Utilities	2,351			(2,351		)	—
	Total derivative assets subject to a master netting agreement or similar arrangement	4,030			(4,030		)	—
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	11			—			11
	Oil and Gas - Crude Options	2			—			2
	Oil and Gas - Natural Gas Basis Swaps	113			—			113
	Utilities	—			—			—
	Total derivative assets not subject to a master netting agreement or similar arrangement	126			—			126
	Total derivative assets	$	4,156		$	(4,030	)	$	126
		As of Sept. 30, 2013
	Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	1,284		$	(1,284	)	$	—
	Oil and Gas - Crude Options	77			(77		)	—
	Oil and Gas - Natural Gas Basis Swaps	181			(181		)	—
	Utilities	10,747			(10,747		)	—
	Interest Rate Swaps	—			—			—
	Total derivative liabilities subject to a master netting agreement or similar arrangement	12,289			(12,289		)	—
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	34			—			34
	Oil and Gas - Crude Options	65			—			65
	Oil and Gas - Natural Gas Basis Swaps	51			—			51
	Utilities	—			—			—
	Interest Rate Swaps	83,142			(5,960		)	77,182
	Total derivative liabilities not subject to a master netting agreement or similar arrangement	83,292			(5,960		)	77,332
	Total derivative liabilities	$	95,581		$	(18,249	)	$	77,332
		As of Dec. 31, 2012
	Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	76		$	—		$	76
	Oil and Gas - Crude Options	93			—			93
	Oil and Gas - Natural Gas Basis Swaps	172			—			172
	Utilities	1,629			(1,586		)	43
	Total derivative assets subject to a master netting agreement or similar arrangement	1,970			(1,586		)	384
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	1,249			—			1,249
	Oil and Gas - Crude Options	285			—			285
	Oil and Gas - Natural Gas Basis Swaps	1,828			—			1,828
	Utilities	—			—			—
	Total derivative assets not subject to a master netting agreement or similar arrangement	3,362			—			3,362
	Total derivative assets	$	5,332		$	(1,586	)	$	3,746
		As of Dec. 31, 2012
	Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	449		$	(449	)	$	—
Oil and Gas - Crude Options	337			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620			(620		)	—
Utilities	10,162			(10,162		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568			(11,568		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52			—			52
Oil and Gas - Crude Options	795			—			795
Oil and Gas - Natural Gas Basis Swaps	507			—			507
Utilities	—			—			—
Interest Rate Swaps	118,088			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442			(5,960		)	113,482
Total derivative liabilities	$	131,010		$	(17,528	)	$	113,482
	As of Sept. 30, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	95		$	—		$	95
Oil and Gas - Crude Options	194			—			194
Oil and Gas - Natural Gas Basis Swaps	5			—			5
Utilities	(2,726		)	15,740			13,014
Total derivative assets subject to a master netting agreement or similar arrangement	(2,432		)	15,740			13,308
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,431			—			1,431
Oil and Gas - Crude Options	425			—			425
Oil and Gas - Natural Gas Basis Swaps	2,066			—			2,066
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,922			—			3,922
Total derivative assets	$	1,490		$	15,740		$	17,230
	As of Sept. 30, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—		$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	—			—			—
Utilities	4,527			—			4,527
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	4,527			—			4,527
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	56			—			56
Oil and Gas - Crude Options	885			—			885
Oil and Gas - Natural Gas Basis Swaps	1,181			—			1,181
Utilities	—			—			—
Interest Rate Swaps	124,580			(3,310		)	121,270
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,702			(3,310		)	123,392
Total derivative liabilities	$	131,229		$	(3,310	)	$	127,919
Offsetting of derivative assets and derivative liabilities on our Consolidated Balance Sheet was as follows (in thousands):
	As of Dec. 31, 2011
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Assets on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	965		$	8,931		$	9,896
Total derivative assets subject to a master netting agreement or similar arrangement	965			8,931			9,896
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,500			—			1,500
Oil and Gas - Natural Gas Basis Swaps	9,158			—			9,158
Total derivative assets not subject to a master netting agreement or similar arrangement	10,658			—			10,658
Total derivative assets	$	11,623		$	8,931		$	20,554
	As of Dec. 31, 2011
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Liabilities on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	17,643		$	(10,487	)	$	7,156
Total derivative liabilities subject to a master netting agreement or similar arrangement	17,643			(10,487		)	7,156
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Options	3,370			—			3,370
Oil and Gas - Natural Gas Basis Swaps	7			—			7
Interest Rate Swaps	122,867			—			122,867
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,244			—			126,244
Total derivative liabilities	$	143,887		$	(10,487	)	$	133,400
Schedule of Collateral Held by Counterparties [Table Text Block]	'
	Derivative assets and derivative liabilities and collateral held by counterparty included in our Condensed Consolidated Balance Sheets were (in thousands):
			As of Sept. 30, 2013
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Asset:
	Oil and Gas	Counterparty A	$	—		$	—		$	—
	Oil and Gas	Counterparty B	126			—			126
	Utilities	Counterparty A	—			—			—
			$	126		$	—		$	126
			As of Sept. 30, 2013
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities
	Oil and Gas	Counterparty A	$	—		$	(355	)	$	(355	)
	Oil and Gas	Counterparty B	150			—			150
	Utilities	Counterparty A	—			(3,333		)	(3,333		)
	Interest Rate Swap	Counterparty D	3,563			—			3,563
	Interest Rate Swap	Counterparty E	19,993			—			19,993
	Interest Rate Swap	Counterparty F	9,858			—			9,858
	Interest Rate Swap	Counterparty G	20,138			—			20,138
	Interest Rate Swap	Counterparty H	8,857			—			8,857
	Interest Rate Swap	Counterparty I	14,773			—			14,773
			$	77,332		$	(3,688	)	$	73,644
			As of Dec. 31, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Assets:
	Oil and Gas	Counterparty A	$	341		$	—		$	341
	Oil and Gas	Counterparty B	3,362			—			3,362
	Utilities	Counterparty A	43			—			43
			$	3,746		$	—		$	3,746
			As of Dec. 31, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities:
	Oil and Gas	Counterparty A	$	—		$	(1,787	)	$	(1,787	)
	Oil and Gas	Counterparty B	1,354			—			1,354
	Utilities	Counterparty A	—			(4,354		)	(4,354		)
	Interest Rate Swap	Counterparty D	4,588			—			4,588
	Interest Rate Swap	Counterparty E	29,245			—			29,245
	Interest Rate Swap	Counterparty F	12,721			—			12,721
	Interest Rate Swap	Counterparty G	26,520			—			26,520
	Interest Rate Swap	Counterparty H	16,809			—			16,809
	Interest Rate Swap	Counterparty I	22,245			—			22,245
			$	113,482		$	(6,141	)	$	107,341
			As of Sept. 30, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Assets:
	Oil and Gas	Counterparty A	$	294		$	(2,414	)	$	(2,120	)
	Oil and Gas	Counterparty B	3,922			—			3,922
	Utilities	Counterparty A	13,014			—			13,014
			$	17,230		$	(2,414	)	$	14,816
			As of Sept. 30, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities:
	Oil and Gas	Counterparty A	$	—		$	—		$	—
	Oil and Gas	Counterparty B	2,122			—			2,122
	Utilities	Counterparty A	4,527			—			4,527
	Interest Rate Swap	Counterparty D	4,903			—			4,903
	Interest Rate Swap	Counterparty E	31,147			—			31,147
	Interest Rate Swap	Counterparty F	13,554			—			13,554
Interest Rate Swap	Counterparty G	27,610			—			27,610
Interest Rate Swap	Counterparty H	20,331			—			20,331
Interest Rate Swap	Counterparty I	23,725			—			23,725
		$	127,919		$	—		$	127,919
Derivative assets and derivative liabilities and collateral held by counterparty on our Consolidated Balance Sheet were (in thousands):
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	10,658			—			10,658
Utilities	Counterparty A	9,896			—			9,896
		$	20,554		$	—		$	20,554
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	3,377			—			3,377
Utilities	Counterparty A	7,156			—			7,156
Interest Rate Swap	Counterparty D	5,140			—			5,140
Interest Rate Swap	Counterparty E	31,095			—			31,095
Interest Rate Swap	Counterparty F	13,880			—			13,880
Interest Rate Swap	Counterparty G	26,329			—			26,329
Interest Rate Swap	Counterparty H	23,203			—			23,203
Interest Rate Swap	Counterparty I	23,220			—			23,220
		$	133,400		$	—		$	133,400
Cash Flow Hedging [Member]	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Schedule of Cash Flow Hedges, Gain (Loss) in Statements of Income and Balance Sheet, Location	'
	The impacts of cash flow hedges on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):
	Three Months Ended Sept. 30, 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		$	(907	)		Interest expense		$	(1,844	)				$	—
	Commodity derivatives		(2,140		)		Revenue		(168		)				—
	Total		$	(3,047	)				$	(2,012	)				$	—
	Three Months Ended Sept. 30, 2012
	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		$	(1,684	)		Interest expense		$	(1,853	)				$	—
	Commodity derivatives		(3,111		)		Revenue		1,838						—
	Total		$	(4,795	)				$	(15	)				$	—
	Nine Months Ended Sept. 30, 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		$	141			Interest expense		$	(5,460	)				$	—
	Commodity derivatives		86				Revenue		896						—
	Total		$	227					$	(4,564	)				$	—
	Nine Months Ended Sept. 30, 2012
	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		$	(4,697	)		Interest expense		$	(5,518	)				$	—
	Commodity derivatives		601				Revenue		7,741						—
	Total		$	(4,096	)				$	2,223					$	—
Not Designated as Hedging Instrument [Member]	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Income and Balance Sheets, Location [Table Text Block]	'
	The impacts of derivative instruments not designated as hedge instruments on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands):
					Three Months Ended				Nine Months Ended
					Sept. 30, 2013				Sept. 30, 2013
	Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
	as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
			Recognized in Income		Recognized in Income				Recognized in Income
	Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	3,144			$	29,393
	Interest rate swaps - realized		Interest expense		(3,300		)		(10,056		)
					$	(156	)		$	19,337
					Three Months Ended				Nine Months Ended
					Sept. 30, 2012				Sept. 30, 2012
	Derivatives Not Designated		Location of Gain/(Loss)		Amount of Gain/(Loss)				Amount of Gain/(Loss)
	as Hedging Instruments		on Derivatives		on Derivatives				on Derivatives
			Recognized in Income		Recognized in Income				Recognized in Income
	Interest rate swaps - unrealized		Unrealized gain (loss) on interest rate swaps, net		$	605			$	(2,902	)
	Interest rate swaps - realized		Interest expense		(3,250		)		(9,697		)
	Commodity derivatives		Revenue		(14		)		(14		)
					$	(2,659	)		$	(12,613	)

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value of Financial Instruments [Abstract]	'
Fair Value of Financial Instruments [Table Text Block]	'
	The estimated fair values of our financial instruments, excluding derivatives which are presented in Note 11, were as follows (in thousands) as of:
		Sept. 30, 2013				Dec. 31, 2012				Sept. 30, 2012
		Carrying		Fair Value		Carrying		Fair Value		Carrying		Fair Value
		Amount				Amount				Amount
	Cash and cash equivalents (a)	$	13,637	$	13,637	$	15,462	$	15,462	$	247,192	$	247,192
	Restricted cash and equivalents (a)	$	6,782	$	6,782	$	7,916	$	7,916	$	7,302	$	7,302
	Notes receivable included in Other current assets(a)	$	—	$	—	$	—	$	—	$	21,832	$	21,832
	Notes payable (a)	$	138,300	$	138,300	$	277,000	$	277,000	$	225,000	$	225,000
	Long-term debt, including current maturities (b)	$	1,211,673	$	1,325,729	$	1,042,850	$	1,231,559	$	1,271,260	$	1,471,932
	__________
	(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.

Sale_of_Assets_Oil_and_Gas_Tab

Sale of Assets Oil and Gas (Tables)	9 Months Ended
	Sep. 30, 2013
Cash proceeds from sale of operating assets [Table Text Block]	'
	Net cash proceeds, subsequent to the true-up of all post-closing adjustments, were as follows (in thousands):
	Cash proceeds received on date of sale	$	243,314
	Adjustments to proceeds:
	Final post close adjustments	2,793
	Transaction adviser fees	(1,400		)
	Payment for contractual obligation related to "back-in" fee *	(16,847		)
	Final net cash proceeds	$	227,860
	_____________
	*	Required payment, triggered by the sale of the property, arising from a contractual obligation contained in the original participation agreement with the property operator.

Part_II_Item_5_Fair_Value_Meas1

Part II, Item 5 - Fair Value Measurements Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Schedule of Derivative Offsetting On Balance Sheet [Table Text Block]	'
	Offsetting of derivative assets and derivative liabilities on our Condensed Consolidated Balance Sheets was as follows:
		As of Sept. 30, 2013
	Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	40		$	(40	)	$	—
	Oil and Gas - Crude Options	—			—			—
	Oil and Gas - Natural Gas Basis Swaps	1,639			(1,639		)	—
	Utilities	2,351			(2,351		)	—
	Total derivative assets subject to a master netting agreement or similar arrangement	4,030			(4,030		)	—
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	11			—			11
	Oil and Gas - Crude Options	2			—			2
	Oil and Gas - Natural Gas Basis Swaps	113			—			113
	Utilities	—			—			—
	Total derivative assets not subject to a master netting agreement or similar arrangement	126			—			126
	Total derivative assets	$	4,156		$	(4,030	)	$	126
		As of Sept. 30, 2013
	Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	1,284		$	(1,284	)	$	—
	Oil and Gas - Crude Options	77			(77		)	—
	Oil and Gas - Natural Gas Basis Swaps	181			(181		)	—
	Utilities	10,747			(10,747		)	—
	Interest Rate Swaps	—			—			—
	Total derivative liabilities subject to a master netting agreement or similar arrangement	12,289			(12,289		)	—
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	34			—			34
	Oil and Gas - Crude Options	65			—			65
	Oil and Gas - Natural Gas Basis Swaps	51			—			51
	Utilities	—			—			—
	Interest Rate Swaps	83,142			(5,960		)	77,182
	Total derivative liabilities not subject to a master netting agreement or similar arrangement	83,292			(5,960		)	77,332
	Total derivative liabilities	$	95,581		$	(18,249	)	$	77,332
		As of Dec. 31, 2012
	Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	76		$	—		$	76
	Oil and Gas - Crude Options	93			—			93
	Oil and Gas - Natural Gas Basis Swaps	172			—			172
	Utilities	1,629			(1,586		)	43
	Total derivative assets subject to a master netting agreement or similar arrangement	1,970			(1,586		)	384
	Not subject to a master netting agreement or similar arrangement:
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	1,249			—			1,249
	Oil and Gas - Crude Options	285			—			285
	Oil and Gas - Natural Gas Basis Swaps	1,828			—			1,828
	Utilities	—			—			—
	Total derivative assets not subject to a master netting agreement or similar arrangement	3,362			—			3,362
	Total derivative assets	$	5,332		$	(1,586	)	$	3,746
		As of Dec. 31, 2012
	Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
		(in thousands)
	Subject to a master netting agreement or similar arrangement
	Commodity derivative:
	Oil and Gas - Crude Basis Swaps	$	449		$	(449	)	$	—
Oil and Gas - Crude Options	337			(337		)	—
Oil and Gas - Natural Gas Basis Swaps	620			(620		)	—
Utilities	10,162			(10,162		)	—
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	11,568			(11,568		)	—
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	52			—			52
Oil and Gas - Crude Options	795			—			795
Oil and Gas - Natural Gas Basis Swaps	507			—			507
Utilities	—			—			—
Interest Rate Swaps	118,088			(5,960		)	112,128
Total derivative liabilities not subject to a master netting agreement or similar arrangement	119,442			(5,960		)	113,482
Total derivative liabilities	$	131,010		$	(17,528	)	$	113,482
	As of Sept. 30, 2012
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Assets on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to master netting agreements or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	95		$	—		$	95
Oil and Gas - Crude Options	194			—			194
Oil and Gas - Natural Gas Basis Swaps	5			—			5
Utilities	(2,726		)	15,740			13,014
Total derivative assets subject to a master netting agreement or similar arrangement	(2,432		)	15,740			13,308
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,431			—			1,431
Oil and Gas - Crude Options	425			—			425
Oil and Gas - Natural Gas Basis Swaps	2,066			—			2,066
Utilities	—			—			—
Total derivative assets not subject to a master netting agreement or similar arrangement	3,922			—			3,922
Total derivative assets	$	1,490		$	15,740		$	17,230
	As of Sept. 30, 2012
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Condensed Consolidated Balance Sheets			Net Amount of Total Derivative Liabilities on Condensed Consolidated Balance Sheets
	(in thousands)
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	$	—		$	—		$	—
Oil and Gas - Crude Options	—			—			—
Oil and Gas - Natural Gas Basis Swaps	—			—			—
Utilities	4,527			—			4,527
Interest Rate Swaps	—			—			—
Total derivative liabilities subject to a master netting agreement or similar arrangement	4,527			—			4,527
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	56			—			56
Oil and Gas - Crude Options	885			—			885
Oil and Gas - Natural Gas Basis Swaps	1,181			—			1,181
Utilities	—			—			—
Interest Rate Swaps	124,580			(3,310		)	121,270
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,702			(3,310		)	123,392
Total derivative liabilities	$	131,229		$	(3,310	)	$	127,919
Offsetting of derivative assets and derivative liabilities on our Consolidated Balance Sheet was as follows (in thousands):
	As of Dec. 31, 2011
Derivative Assets	Gross Amounts of Derivative Assets			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Assets on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	965		$	8,931		$	9,896
Total derivative assets subject to a master netting agreement or similar arrangement	965			8,931			9,896
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Basis Swaps	1,500			—			1,500
Oil and Gas - Natural Gas Basis Swaps	9,158			—			9,158
Total derivative assets not subject to a master netting agreement or similar arrangement	10,658			—			10,658
Total derivative assets	$	11,623		$	8,931		$	20,554
	As of Dec. 31, 2011
Derivative Liabilities	Gross Amounts of Derivative Liabilities			Gross Amounts Offset on Consolidated Balance Sheet			Net Amount of Total Derivative Liabilities on Consolidated Balance Sheet
Subject to a master netting agreement or similar arrangement:
Commodity derivative:
Utilities	$	17,643		$	(10,487	)	$	7,156
Total derivative liabilities subject to a master netting agreement or similar arrangement	17,643			(10,487		)	7,156
Not subject to a master netting agreement or similar arrangement:
Commodity derivative:
Oil and Gas - Crude Options	3,370			—			3,370
Oil and Gas - Natural Gas Basis Swaps	7			—			7
Interest Rate Swaps	122,867			—			122,867
Total derivative liabilities not subject to a master netting agreement or similar arrangement	126,244			—			126,244
Total derivative liabilities	$	143,887		$	(10,487	)	$	133,400
Schedule of Collateral Held by Counterparties [Table Text Block]	'
	Derivative assets and derivative liabilities and collateral held by counterparty included in our Condensed Consolidated Balance Sheets were (in thousands):
			As of Sept. 30, 2013
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Asset:
	Oil and Gas	Counterparty A	$	—		$	—		$	—
	Oil and Gas	Counterparty B	126			—			126
	Utilities	Counterparty A	—			—			—
			$	126		$	—		$	126
			As of Sept. 30, 2013
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities
	Oil and Gas	Counterparty A	$	—		$	(355	)	$	(355	)
	Oil and Gas	Counterparty B	150			—			150
	Utilities	Counterparty A	—			(3,333		)	(3,333		)
	Interest Rate Swap	Counterparty D	3,563			—			3,563
	Interest Rate Swap	Counterparty E	19,993			—			19,993
	Interest Rate Swap	Counterparty F	9,858			—			9,858
	Interest Rate Swap	Counterparty G	20,138			—			20,138
	Interest Rate Swap	Counterparty H	8,857			—			8,857
	Interest Rate Swap	Counterparty I	14,773			—			14,773
			$	77,332		$	(3,688	)	$	73,644
			As of Dec. 31, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Assets:
	Oil and Gas	Counterparty A	$	341		$	—		$	341
	Oil and Gas	Counterparty B	3,362			—			3,362
	Utilities	Counterparty A	43			—			43
			$	3,746		$	—		$	3,746
			As of Dec. 31, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities:
	Oil and Gas	Counterparty A	$	—		$	(1,787	)	$	(1,787	)
	Oil and Gas	Counterparty B	1,354			—			1,354
	Utilities	Counterparty A	—			(4,354		)	(4,354		)
	Interest Rate Swap	Counterparty D	4,588			—			4,588
	Interest Rate Swap	Counterparty E	29,245			—			29,245
	Interest Rate Swap	Counterparty F	12,721			—			12,721
	Interest Rate Swap	Counterparty G	26,520			—			26,520
	Interest Rate Swap	Counterparty H	16,809			—			16,809
	Interest Rate Swap	Counterparty I	22,245			—			22,245
			$	113,482		$	(6,141	)	$	107,341
			As of Sept. 30, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
	Assets:
	Oil and Gas	Counterparty A	$	294		$	(2,414	)	$	(2,120	)
	Oil and Gas	Counterparty B	3,922			—			3,922
	Utilities	Counterparty A	13,014			—			13,014
			$	17,230		$	(2,414	)	$	14,816
			As of Sept. 30, 2012
						Gross Amounts Not Offset on Condensed Consolidated Balance Sheets
	Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
	Liabilities:
	Oil and Gas	Counterparty A	$	—		$	—		$	—
	Oil and Gas	Counterparty B	2,122			—			2,122
	Utilities	Counterparty A	4,527			—			4,527
	Interest Rate Swap	Counterparty D	4,903			—			4,903
	Interest Rate Swap	Counterparty E	31,147			—			31,147
	Interest Rate Swap	Counterparty F	13,554			—			13,554
Interest Rate Swap	Counterparty G	27,610			—			27,610
Interest Rate Swap	Counterparty H	20,331			—			20,331
Interest Rate Swap	Counterparty I	23,725			—			23,725
		$	127,919		$	—		$	127,919
Derivative assets and derivative liabilities and collateral held by counterparty on our Consolidated Balance Sheet were (in thousands):
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Assets			Cash Collateral Received			Net Amount with Counterparty
Asset:
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	10,658			—			10,658
Utilities	Counterparty A	9,896			—			9,896
		$	20,554		$	—		$	20,554
		As of Dec. 31, 2011
					Gross Amounts Not Offset on Consolidated Balance Sheet
Contract Type		Net Amount of Total Derivative Liabilities			Cash Collateral Posted			Net Amount with Counterparty
Liabilities
Oil and Gas	Counterparty A	$	—		$	—		$	—
Oil and Gas	Counterparty B	3,377			—			3,377
Utilities	Counterparty A	7,156			—			7,156
Interest Rate Swap	Counterparty D	5,140			—			5,140
Interest Rate Swap	Counterparty E	31,095			—			31,095
Interest Rate Swap	Counterparty F	13,880			—			13,880
Interest Rate Swap	Counterparty G	26,329			—			26,329
Interest Rate Swap	Counterparty H	23,203			—			23,203
Interest Rate Swap	Counterparty I	23,220			—			23,220
		$	133,400		$	—		$	133,400

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Non-cash Investing and Financing Activities from Continuing Operations [Abstract]	'	'
Property, plant and equipment acquired wtih accrued liabilities	$47,214	$39,303
Increase (decrease) in capitalized assets associated with asset retirement obligations	0	3,806
Cash (paid) refunded during the period for continuing operations [Abstract]	'	'
Interest (net of amounts capitalized)	-57,175	-69,901
Income taxes, net	($4,924)	$425

Materials_Supplies_and_Fuel_De

Materials, Supplies and Fuel (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Thousands, unless otherwise specified
Inventory, Net [Abstract]	'	'	'
Materials and supplies	$50,564	$43,397	$43,847
Fuel - Electric Utilities	6,384	8,589	8,289
Natural gas in storage held for distribution	38,282	25,657	28,764
Total materials, supplies and fuel	$95,230	$77,643	$80,900

Accounts_Receivable_Details

Accounts Receivable (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Thousands, unless otherwise specified
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	($1,209)	($768)	($912)
Accounts receivable, net	114,137	163,698	104,482
Corporate [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	2,226	799	657
Electric Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	-648	-527	-603
Accounts receivable, net	68,759	77,798	64,640
Gas Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	-542	-222	-204
Accounts receivable, net	32,028	71,235	27,474
Power Generation [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	3	16	4
Coal Mining [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	0	0	0
Accounts receivable, net	2,677	2,247	1,540
Oil and Gas [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Allowance for Doubtful Accounts Receivable	-19	-19	-105
Accounts receivable, net	8,444	11,603	10,167
Billed Revenues [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	83,316	100,661	77,473
Billed Revenues [Member] | Corporate [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	2,226	799	657
Billed Revenues [Member] | Electric Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	49,254	54,482	46,802
Billed Revenues [Member] | Gas Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	20,693	31,495	18,198
Billed Revenues [Member] | Power Generation [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	3	16	4
Billed Revenues [Member] | Coal Mining [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	2,677	2,247	1,540
Billed Revenues [Member] | Oil and Gas [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	8,463	11,622	10,272
Unbilled Revenues [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	32,030	63,805	27,921
Unbilled Revenues [Member] | Corporate [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] | Electric Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	20,153	23,843	18,441
Unbilled Revenues [Member] | Gas Utilities [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	11,877	39,962	9,480
Unbilled Revenues [Member] | Power Generation [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] | Coal Mining [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] | Oil and Gas [Member]	'	'	'
Accounts Receivable [Line Items]	'	'	'
Accounts Receivable, Trade	$0	$0	$0

Notes_Payable_and_Long_Term_De

Notes Payable and Long Term Debt (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Thousands, unless otherwise specified
Line of Credit Facility [Line Items]	'	'	'
Notes payable	$138,300	$277,000	$225,000
Letters of Credit Outstanding, Amount	53,137	36,300	36,300
Line of Credit [Member]	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Notes payable	138,300	127,000	75,000
Letters of Credit Outstanding, Amount	53,137	36,300	36,300
Debt Disclosure [Abstract]	'	'	'
Recourse Leverage Ratio	52.00%	'	'
Recourse Leverage Ratio, Maximum Allowed, Covenant	65.00%	'	'
Loans Payable [Member]	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Notes payable	0	150,000	150,000
Letters of Credit Outstanding, Amount	$0	$0	$0

Notes_Payable_and_LongTerm_Deb2

Notes Payable and Long-Term Debt Replacement of Notes Payable and Long-term Term Loan (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Jun. 21, 2013
Long Term Loan due September 2013 [Member]	'	'
Debt Instrument [Line Items]	'	'
Long-term Debt, Gross	'	$275,000,000
Debt Instrument, Maturity Date	19-Jun-15	'
Corporate Term Loan due September 2013 [Member]	'	'
Debt Instrument [Line Items]	'	'
Extinguishment of Debt, Amount	100,000,000	'
Corporate Term Loan due September 2013 [Member] | LIBOR [Member]	'	'
Debt Instrument [Line Items]	'	'
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.31%	'
Debt Instrument, Basis Spread on Variable Rate	1.13%	'
Loans Payable [Member]	'	'
Debt Instrument [Line Items]	'	'
Notes payable	150,000,000	'
Line of Credit [Member]	'	'
Debt Instrument [Line Items]	'	'
Notes payable	25,000,000	'

Earnings_Per_Share_Basic_to_Di

Earnings Per Share Basic to Dilutive EPS (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income (Loss) from Continuing Operations Attributable to Parent	$23,124	$34,623	$96,839	$57,571
Weighted Average Shares, Basic	44,201	43,847	44,143	43,792
Dilutive Effect on Basic Earnings Per Share [Abstract]	'	'	'	'
Other Dilutive Effects, Shares	112	74	102	61
Weighted Average Shares, Diluted	44,457	44,108	44,395	44,026
Restricted Stock [Member]	'	'	'	'
Dilutive Effect on Basic Earnings Per Share [Abstract]	'	'	'	'
Restricted Stock and Restricted Stock Units, Shares	131	175	137	159
Stock Options [Member]	'	'	'	'
Dilutive Effect on Basic Earnings Per Share [Abstract]	'	'	'	'
Restricted Stock and Restricted Stock Units, Shares	13	12	13	14

Earnings_Per_Share_Antidilutiv

Earnings Per Share Anti-dilutive shares (Details)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	138	9	173
Stock Options [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	77	9	101
Restricted Stock [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	61	0	53
Other Stock [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	0	0	19

Other_Comprehensive_Income_Oth1

Other Comprehensive Income Other Comprehensive Income (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Interest expense	($23,840)	($27,475)	($70,881)	($85,151)
Revenue	259,907	246,808	920,404	855,022
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes	36,458	52,515	147,452	87,640
Income tax benefit (expense)	-13,334	-17,914	-50,527	-30,057
Cash Flow Hedging [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Income (loss) from continuing operations before earnings (loss) of unconsolidated subsidiaries and income taxes	2,012	15	4,564	-2,223
Income tax benefit (expense)	-586	13	-1,469	890
Net income (loss) available for common stock	1,426	28	3,095	-1,333
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	1,844	1,853	5,460	5,518
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	168	-1,838	-896	-7,741
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] | Utilities - Operations and maintenance [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Reclassification from Accumulated Other Comprehensive income, Current Period, before Tax	-31	0	-93	0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] | Non-regulated energy operations and maintenance [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Reclassification from Accumulated Other Comprehensive income, Current Period, before Tax	-32	0	-96	0
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Utilities - Operations and maintenance [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Reclassification from Accumulated Other Comprehensive income, Current Period, before Tax	425	0	1,267	0
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Non-regulated energy operations and maintenance [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Reclassification from Accumulated Other Comprehensive income, Current Period, before Tax	275	0	823	0
Accumulated Defined Benefit Plans Adjustment [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Reclassification from Accumulated Other Comprehensive income, Current Period, before Tax	637	0	1,901	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Tax	-220	0	-663	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$417	$0	$1,238	$0

Other_Comprehensive_Income_Acc

Other Comprehensive Income Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended						9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), Net of Tax	($31,021)	($30,781)	($36,224)	($37,215)	($33,652)	($33,044)	($31,021)	($37,215)	($35,488)	($32,878)
Other Comprehensive Income (Loss), Net of Tax	-240	5,443	-736	-3,563	-608	-166	4,467	-4,337	'	'
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	'	'	'	'	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), Net of Tax	-12,484	-11,827	-16,906	-18,139	-14,576	-13,968	-12,484	-18,139	-15,713	-13,802
Other Comprehensive Income (Loss), Net of Tax	-657	5,079	-1,193	-3,563	-608	-166	'	'	'	'
Accumulated Defined Benefit Plans Adjustment [Member]	'	'	'	'	'	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), Net of Tax	-18,537	-18,954	-19,318	-19,076	-19,076	-19,076	-18,537	-19,076	-19,775	-19,076
Other Comprehensive Income (Loss), Net of Tax	$417	$364	$457	$0	$0	$0	'	'	'	'

Employee_Benefit_Plans_Employe1

Employee Benefit Plans Employee Benefit Plans (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Pension Plan [Member]	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'
Service Cost	$1,608	$1,431	$4,824	$4,291
Interest Cost	3,825	3,688	11,475	11,062
Expected Return on Plan Assets	-4,654	-4,084	-13,962	-12,252
Prior Service Cost (Benefit)	16	22	48	66
Net Loss (Gain)	3,062	2,408	9,186	7,224
Net Periodic Benefit Cost	3,857	3,465	11,571	10,391
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Estimated Future Employer Contributions In Current Fiscal Year	'	'	0	'
Estimated Future Employer Contributions in Next Fiscal Year	'	'	12,500	'
Non-pension Defined Benefit Postretirement Healthcare Plans [Member]	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'
Service Cost	419	402	1,257	1,206
Interest Cost	417	523	1,251	1,569
Expected Return on Plan Assets	-20	-19	-60	-57
Prior Service Cost (Benefit)	-125	-125	-375	-375
Net Loss (Gain)	121	222	363	666
Net Periodic Benefit Cost	812	1,003	2,436	3,009
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Estimated Future Employer Contributions In Current Fiscal Year	'	'	784	'
Estimated Future Employer Contributions in Next Fiscal Year	'	'	3,350	'
Supplemenatal Non-qualified Defined Benefit Plans [Member]	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'
Service Cost	348	243	1,044	735
Interest Cost	332	331	996	993
Prior Service Cost (Benefit)	1	1	3	3
Net Loss (Gain)	198	202	594	606
Net Periodic Benefit Cost	879	777	2,637	2,337
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Estimated Future Employer Contributions In Current Fiscal Year	'	'	322	'
Estimated Future Employer Contributions in Next Fiscal Year	'	'	1,463	'
Scenario, Actual [Member] | Defined Benefit Pension Plan [Member]	'	'	'	'
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Contributions Made by Employer	12,500	'	12,500	'
Scenario, Actual [Member] | Non-pension Defined Benefit Postretirement Healthcare Plans [Member]	'	'	'	'
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Contributions Made by Employer	784	'	2,352	'
Scenario, Actual [Member] | Supplemenatal Non-qualified Defined Benefit Plans [Member]	'	'	'	'
Pension and Other Postretirement Benefit Contributions [Abstract]	'	'	'	'
Contributions Made by Employer	$322	'	$966	'

Business_Segment_Information_I

Business Segment Information Information Relating to Segment Statement of Income (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	$259,907,000		$246,808,000		$920,404,000		$855,022,000
Intersegment Operating Revenue	0		0		0		0
Income (Loss) from Continuing Operations	23,124,000		34,623,000		96,839,000		57,571,000
Mark-to-market gain (loss) on certain interest rate swaps, net of tax	2,000,000		400,000		19,100,000		-1,900,000
Impairment of Oil and Gas Properties, Net of Tax	'		'		'		17,300,000
Overhead Of Discontinued Operations, Net of Tax	'		'		'		1,600,000
Corporate [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	0		0		0		0
Intersegment Operating Revenue	0		0		0		0
Income (Loss) from Continuing Operations	2,310,000	[1]	-4,160,000	[1]	19,688,000	[1]	-13,949,000	[1],[2]
Intersegment Elimination [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	0		0		0		0
Intersegment Operating Revenue	-31,000,000		-31,998,000		-92,357,000		-92,338,000
Income (Loss) from Continuing Operations	0		0		0		0
Electric Utilities [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	169,401,000		151,281,000		482,222,000		451,974,000
Intersegment Operating Revenue	2,003,000		3,736,000		9,844,000		11,946,000
Income (Loss) from Continuing Operations	15,097,000		14,573,000		38,063,000		37,478,000
Gas Utilities [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	67,792,000		63,435,000		373,440,000		314,343,000
Intersegment Operating Revenue	0		0		0		0
Income (Loss) from Continuing Operations	-1,450,000		3,000		20,225,000		16,369,000
Power Generation [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	1,575,000		1,256,000		3,628,000		3,193,000
Intersegment Operating Revenue	20,393,000		19,695,000		58,825,000		56,119,000
Income (Loss) from Continuing Operations	6,707,000		5,128,000		17,382,000		15,968,000
Coal Mining [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	6,713,000		6,108,000		19,530,000		18,518,000
Intersegment Operating Revenue	8,604,000		8,567,000		23,688,000		24,273,000
Income (Loss) from Continuing Operations	2,142,000		1,690,000		5,180,000		3,924,000
Oil and Gas [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
External Operating Revenue	14,426,000		24,728,000		41,584,000		66,994,000
Intersegment Operating Revenue	0		0		0		0
Income (Loss) from Continuing Operations	-1,682,000		17,389,000	[3]	-3,699,000		-2,219,000	[3]
Williston Basin Assets [Member] | Oil and Gas [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Gain (Loss) on Sale of Property Plant Equipment, Net of Tax	'		'		'		($17,700,000)
[1]	Income (loss) from continuing operations includes a $2.0 million and a $19.1 million net after-tax non-cash mark-to-market gain on certain interest rate swaps for the three and nine months ended Sept. 30, 2013, respectively, and a $0.4 million after-tax non-cash mark-to-market gain and a $1.9 million net after-tax non-cash mark-to-market loss for the three and nine months ended Sept. 30, 2012, respectively, for those same interest rate swaps.
[2]	Certain indirect corporate costs and inter-segment interest expense after-tax totaling $1.6 million for the nine months ended Sept. 30, 2012, were included in the Corporate activities in continuing operations and were not reclassified as discontinued operations.
[3]	Income (loss) from continuing operations for the nine months ended Sept. 30, 2012, includes a $17.3 million non-cash after-tax ceiling test impairment charge. Income (loss) from continuing operations for the three and nine months ended Sept. 30, 2012, includes an after-tax gain of $17.7 million relating to the sale of the Williston Basin assets. See Notes 14 and 15 for further information.

Business_Segment_Information_S

Business Segment Information Segment and Corporate Assets (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Thousands, unless otherwise specified
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	$3,801,240		$3,729,471		$3,853,628
Corporate [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	130,100		115,408		367,557
Electric Utilities [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	2,464,123	[1]	2,387,458	[1]	2,302,951	[1]
Gas Utilities [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	757,746		765,165		710,099
Power Generation [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	102,331	[1]	119,170	[1]	119,489	[1]
Coal Mining [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	82,155		83,810		90,444
Oil and Gas [Member]	'		'		'
Segment Reporting, Asset Reconciling Item [Line Items]	'		'		'
Assets	$264,785		$258,460		$263,088
[1]	The PPA pertaining to the portion of the Pueblo Airport Generation Station owned by Colorado IPP that supports Colorado Electric customers is accounted for as a capital lease. Therefore, assets owned by the Power Generation segment are included in Total assets of Electric Utilities Segment under this accounting for a capital lease.

Risk_Management_Activities_Det

Risk Management Activities (Details) (USD $)	9 Months Ended				12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Derivative [Line Items]	'		'		'
Credit Exposure, Non-Investment Grade Company	$1,300,000		'		'
Derivative assets, current	126,000		16,063,000		3,236,000
Derivative assets, non-current	0		1,167,000		510,000
Derivative liabilities, current	65,944,000		86,509,000		96,541,000
Derivative liabilities, non-current	11,388,000		41,410,000		16,941,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative liabilities, current	7,039,000		7,028,000		7,039,000
Derivative liabilities, non-current	11,388,000		18,660,000		16,941,000
Derivative, Remaining Maturity	'3 years 3 months		'4 years 3 months		'4 years
Notional Amount, Interest Rate Derivatives	150,000,000	[1]	150,000,000	[1]	150,000,000	[1]
Weighted Average Fixed Interest Rate	5.04%		5.04%		5.04%
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	-7,000,000		'		'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative liabilities, current	58,755,000		77,914,000		88,148,000
Derivative liabilities, non-current	0		17,668,000		0
Derivative, Remaining Maturity	'0 years 3 months		'1 year 3 months		'1 year
Notional Amount, Interest Rate Derivatives	250,000,000	[2]	250,000,000	[2]	250,000,000	[2]
Weighted Average Fixed Interest Rate	5.67%		5.67%		5.67%
Derivative, Fair Value, Amount Offset Against Collateral, Net	6,000,000		'		'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Dedesignated Interest Rate Swap Expiring 2018 [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Remaining Maturity	'5 years 3 months		'		'
Notional Amount, Interest Rate Derivatives	100,000,000		'		'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Dedesignated Interest Rate Swaps Expiring 2028 [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Remaining Maturity	'15 years 3 months		'		'
Notional Amount, Interest Rate Derivatives	150,000,000		'		'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Credit Risk [Member]	'		'		'
Derivative [Line Items]	'		'		'
Notional Amount, Interest Rate Derivatives	50,000,000		'		'
Potential Future Exposure on Credit Related Contingent Feature	20,000,000		'		'
Black Hills Corporation [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Notional Amount, Interest Rate Derivatives	75,000,000		'		'
Utilities Group [Member] | Natural Gas, Distribution [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative assets, current	0		12,380,000		0
Derivative assets, non-current	0		634,000		43,000
Derivative liabilities, non-current	0		4,527,000		0
Net Unrealized (Gain) Loss Included in Regulatory assets or Regulatory liabilities	10,652,000		9,318,000		9,596,000
Utilities Group [Member] | Future [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	14,010,000		14,690,000		15,350,000
Derivative, Remaining Maturity	'74 months		'75 months		'83 months
Utilities Group [Member] | Commodity Option [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	6,810,000		5,560,000		2,430,000
Derivative, Remaining Maturity	'6 months		'6 months		'2 months
Utilities Group [Member] | Basis Swap [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	9,790,000		8,800,000		12,020,000
Derivative, Remaining Maturity	'63 months		'75 months		'72 months
Oil and Gas [Member]	'		'		'
Derivative [Line Items]	'		'		'
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	100,000		'		'
Oil and Gas [Member] | Swaps, Options and Futures [Member] | Crude Oil [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	499,500	[3]	537,000	[3]	528,000	[3]
Maximum Length of Time Hedged in Cash Flow Hedge	'0 years 3 months	[4]	'1 year	[4]	'1 year	[4]
Derivative assets, current	13,000		1,651,000		1,405,000
Derivative assets, non-current	0		494,000		297,000
Derivative liabilities, current	98,000		527,000		847,000
Derivative liabilities, non-current	0		414,000		0
Oil and Gas [Member] | Swaps and Futures [Member] | Natural Gas [Member]	'		'		'
Derivative [Line Items]	'		'		'
Derivative, Nonmonetary Notional Amount	9,874,000	[3]	7,455,250	[3]	8,215,500	[3]
Maximum Length of Time Hedged in Cash Flow Hedge	'1 month	[4]	'1 year	[4]	'0 years 9 months	[4]
Derivative assets, current	113,000		2,032,000		1,831,000
Derivative assets, non-current	0		39,000		170,000
Derivative liabilities, current	52,000		1,040,000		507,000
Derivative liabilities, non-current	0		141,000		0
Power Generation [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]	'		'		'
Derivative [Line Items]	'		'		'
Notional Amount, Interest Rate Derivatives	$75,000,000		'		'
[1]	These swaps have been designated to $75.0 million of borrowings on our Revolving Credit Facility and $75.0 million of borrowings on our project financing debt at Black Hills Wyoming. The swaps that hedge the variable rate debt at Black Hills Wyoming were transferred from BHC. Both BHC and Black Hills Wyoming are jointly and severally obligated for the swaps’ obligations. These swaps are priced using three-month LIBOR, matching the floating portion of the related swaps.
[2]	Maximum terms in years reflect the amended early termination dates. If the early termination dates are not extended, the swaps will require cash settlement based on the swap value on the termination date. If extended, de-designated swaps totaling $100.0 million notional terminate in approximately 5.25 years and de-designated swaps totaling $150.0 million notional terminate in approximately 15.25 years.
[3]	Crude oil in Bbls, natural gas in MMBtus.
[4]	Refers to the term of the derivative instrument. Assets and liabilities are classified as current/non-current based on the term of the hedged transaction and the corresponding settlement of the derivative instrument.

Fair_Value_Measurements_Fair_V1

Fair Value Measurements Fair Value Hierarchy (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012		Sep. 30, 2012		Dec. 31, 2011
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	$126	$3,746		$17,230		$20,554
Assets, Fair Value Disclosure	126	'		17,230		'
Liabilities, Fair Value Disclosure	77,332	'		127,919		'
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 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Assets, Fair Value Disclosure	'	3,746		'		'
Liabilities, Fair Value Disclosure	'	113,482		'		'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Assets, Fair Value Disclosure	13,637	0		0		'
Liabilities, Fair Value Disclosure	0	0		0		'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Assets, Fair Value Disclosure	4,156	3,703		1,456		'
Liabilities, Fair Value Disclosure	95,581	131,010		131,229		'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Assets, Fair Value Disclosure	0	43		34		'
Liabilities, Fair Value Disclosure	0	0		0		'
Fair Value, Measurements, Recurring [Member] | Netting [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Assets, Fair Value Disclosure	-4,030	0		15,740		'
Liabilities, Fair Value Disclosure	-18,249	-17,528		-3,310		'
Interest Rate Swap [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	77,182	'		121,270		'
Interest Rate Swap [Member] | Fair Value [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	'	112,128		'		'
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	0	0		0		'
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	83,142	118,088		124,580		'
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	0	0		0		'
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Liabilities	-5,960	-5,960		-3,310		'
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	2	'		619		'
Derivative Liabilities	65	'		885		'
Crude Oil [Member] | Commodity Option [Member] | Fair Value [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	'	378		'		'
Derivative Liabilities	'	795		'		'
Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	2	378		619		'
Derivative Liabilities	142	1,131		885		'
Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	-77	-336		0		'
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	11	'		1,526		'
Derivative Liabilities	34	'		56		'
Crude Oil [Member] | Basis Swap [Member] | Fair Value [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	'	1,325		'		'
Derivative Liabilities	'	52		'		'
Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	51	1,325		1,526		'
Derivative Liabilities	1,318	502		56		'
Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	-40	0		0		'
Derivative Liabilities	-1,284	-450		0		'
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		'
Derivative Liabilities	0	'		0		'
Natural Gas [Member] | Commodity Option [Member] | Fair Value [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	'	0		'		'
Derivative Liabilities	'	0		'		'
Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
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	113	'		2,071		'
Derivative Liabilities	51	'		1,181		'
Natural Gas [Member] | Basis Swap [Member] | Fair Value [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	'	2,000		'		'
Derivative Liabilities	'	507		'		'
Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	1,752	2,000		2,071		'
Derivative Liabilities	232	1,127		1,181		'
Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Oil and Gas [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	-1,639	0		0		'
Derivative Liabilities	-181	-620		0		'
Natural Gas, Distribution [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	'		13,014		'
Derivative Liabilities	0	'		4,527		'
Natural Gas, Distribution [Member] | Fair Value [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	'	43		'		'
Derivative Liabilities	'	0		'		'
Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	0		0		'
Derivative Liabilities	0	0		0		'
Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	2,351	0		-2,760		'
Derivative Liabilities	10,747	10,162		4,527		'
Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	0	43	[1]	34	[1]	'
Derivative Liabilities	0	0		0		'
Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Netting [Member] | Utilities Group [Member]	'	'		'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'		'		'
Derivative Assets	-2,351	0		15,740		'
Derivative Liabilities	($10,747)	($10,162)		$0		'
[1]	The significant unobservable inputs used in the fair value measurement of the long-term OTC contracts are based on the average of price quotes from an independent third party market participant and the OTC contract broker. The unobservable inputs are long-term natural gas prices. Significant changes to these inputs along with the contract term would impact the derivative asset/liability and regulatory asset/liability, but will not impact the results of operations until the contract is settled under the original terms of the contract. The contracts will be classified as Level 2 once settlement is within 60 months of maturity and quoted market prices from a market exchange are available.

Fair_Value_Measurements_Fair_V2

Fair Value Measurements Fair Value Measurements Balance Sheet Location (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	$4,156	$5,332	$1,490	$11,623
Derivative Liability, Fair Value, Gross Liability	95,581	131,010	131,229	143,887
Designated as Hedging Instrument [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Net	1,805	3,384	3,796	'
Derivative Liability, Fair Value, Net	20,119	26,793	27,779	'
Not Designated as Hedging Instrument [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Net	0	1,948	421	'
Derivative Liability, Fair Value, Net	73,111	104,218	106,177	'
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Assets, Current [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	846	2,874	3,263	'
Derivative Asset, Fair Value, Gross Liability	0	0	0	'
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Assets, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	959	510	533	'
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	1,317	1,993	1,534	'
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	0	0	'
Derivative Liability, Fair Value, Gross Liability	375	821	555	'
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Assets, Current [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	362	421	'
Derivative Asset, Fair Value, Gross Liability	0	0	3,361	'
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Assets, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	0	0	'
Derivative Asset, Fair Value, Gross Liability	0	0	-634	'
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Current [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	1,180	0	'
Derivative Liability, Fair Value, Gross Liability	1,795	4,957	33	'
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	406	0	'
Derivative Liability, Fair Value, Gross Liability	6,601	5,153	4,527	'
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	7,039	7,038	7,029	'
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	0	0	'
Derivative Liability, Fair Value, Gross Liability	11,388	16,941	18,661	'
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Current [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	0	0	'
Derivative Liability, Fair Value, Gross Liability	64,715	94,108	77,913	'
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Noncurrent [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Liability, Fair Value, Gross Asset	0	0	0	'
Derivative Liability, Fair Value, Gross Liability	$0	$0	$20,977	'

Fair_Value_Measurements_Fair_V3

Fair Value Measurements Fair Value Balance Sheet Offsetting (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	$4,156	$5,332	$1,490	$11,623
Gross Amounts Offset In Statement Of Financial Position Assets	-4,030	-1,586	15,740	8,931
Derivative Assets	126	3,746	17,230	20,554
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	95,581	131,010	131,229	143,887
Gross Amounts Offset In Statement Of Financial Position Liabilities	-18,249	-17,528	-3,310	-10,487
Derivative Liabilities	77,332	113,482	127,919	133,400
Contract Subject To Master Netting Arrangement [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	4,030	1,970	-2,432	965
Gross Amounts Offset In Statement Of Financial Position Assets	-4,030	-1,586	15,740	8,931
Derivative Assets	0	384	13,308	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	12,289	11,568	4,527	17,643
Gross Amounts Offset In Statement Of Financial Position Liabilities	-12,289	-11,568	0	-10,487
Derivative Liabilities	0	0	4,527	7,156
Contract Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	40	76	95	'
Gross Amounts Offset In Statement Of Financial Position Assets	-40	0	0	'
Derivative Assets	0	76	95	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	1,284	449	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-1,284	-449	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Natural Gas [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	1,639	172	5	'
Gross Amounts Offset In Statement Of Financial Position Assets	-1,639	0	0	'
Derivative Assets	0	172	5	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	181	620	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-181	-620	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Commodity Option [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	93	194	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	0	93	194	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	77	337	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-77	-337	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	2,351	1,629	-2,726	965
Gross Amounts Offset In Statement Of Financial Position Assets	-2,351	-1,586	15,740	8,931
Derivative Assets	0	43	13,014	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	10,747	10,162	4,527	17,643
Gross Amounts Offset In Statement Of Financial Position Liabilities	-10,747	-10,162	0	-10,487
Derivative Liabilities	0	0	4,527	7,156
Contract Subject To Master Netting Arrangement [Member] | Interest Rate Swap [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	0	0	0	'
Contract Not Subject To Master Netting Arrangement [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	126	3,362	3,922	10,658
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	126	3,362	3,922	10,658
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	83,292	119,442	126,702	126,244
Gross Amounts Offset In Statement Of Financial Position Liabilities	-5,960	-5,960	-3,310	0
Derivative Liabilities	77,332	113,482	123,392	126,244
Contract Not Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	11	1,249	1,431	1,500
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	11	1,249	1,431	1,500
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	34	52	56	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	34	52	56	'
Contract Not Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Natural Gas [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	113	1,828	2,066	9,158
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	113	1,828	2,066	9,158
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	51	507	1,181	7
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	0
Derivative Liabilities	51	507	1,181	7
Contract Not Subject To Master Netting Arrangement [Member] | Commodity Option [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	2	285	425	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	2	285	425	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	65	795	885	3,370
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	0
Derivative Liabilities	65	795	885	3,370
Contract Not Subject To Master Netting Arrangement [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	0	0	0	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	0	0	0	'
Contract Not Subject To Master Netting Arrangement [Member] | Interest Rate Swap [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	83,142	118,088	124,580	122,867
Gross Amounts Offset In Statement Of Financial Position Liabilities	-5,960	-5,960	-3,310	0
Derivative Liabilities	$77,182	$112,128	$121,270	$122,867

Fair_Value_Measurements_Fair_V4

Fair Value Measurements Fair Value Balance Sheet Offsetting by Counterparty (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	$126	$3,746	$17,230	$20,554
Derivative, Collateral, Obligation to Return Cash	0	0	-2,414	0
Net Amount with Counterparty, after cash collateral and netting	126	3,746	14,816	20,554
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	77,332	113,482	127,919	133,400
Derivative, Collateral, Right to Reclaim Cash	-3,688	-6,141	0	0
Net Amount with Counterparty, after collateral and netting	73,644	107,341	127,919	133,400
Counterparty D [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	3,563	4,588	4,903	5,140
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	3,563	4,588	4,903	5,140
Counterparty E [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	19,993	29,245	31,147	31,095
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	19,993	29,245	31,147	31,095
Counterparty F [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	9,858	12,721	13,554	13,880
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	9,858	12,721	13,554	13,880
Counterparty G [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	20,138	26,520	27,610	26,329
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	20,138	26,520	27,610	26,329
Counterparty H [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	8,857	16,809	20,331	23,203
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	8,857	16,809	20,331	23,203
Counteryparty I [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	14,773	22,245	23,725	23,220
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	14,773	22,245	23,725	23,220
Utilities Group [Member] | Counterparty A [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	0	43	13,014	9,896
Derivative, Collateral, Obligation to Return Cash	0	0	0	0
Net Amount with Counterparty, after cash collateral and netting	0	43	13,014	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	0	0	4,527	7,156
Derivative, Collateral, Right to Reclaim Cash	-3,333	-4,354	0	0
Net Amount with Counterparty, after collateral and netting	-3,333	-4,354	4,527	7,156
Oil and Gas [Member] | Counterparty A [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	0	341	294	0
Derivative, Collateral, Obligation to Return Cash	0	0	-2,414	0
Net Amount with Counterparty, after cash collateral and netting	0	341	-2,120	0
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	0	0	0	0
Derivative, Collateral, Right to Reclaim Cash	-355	-1,787	0	0
Net Amount with Counterparty, after collateral and netting	-355	-1,787	0	0
Oil and Gas [Member] | Counterparty B [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	126	3,362	3,922	10,658
Derivative, Collateral, Obligation to Return Cash	0	0	0	0
Net Amount with Counterparty, after cash collateral and netting	126	3,362	3,922	10,658
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	150	1,354	2,122	3,377
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	$150	$1,354	$2,122	$3,377

Fair_Value_Measurements_Fair_V5

Fair Value Measurements Fair Value Measurements Hedging Activities (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments Not Designated as Hedging Instruments [Abstract]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	($156)	($2,659)	$19,337	($12,613)
Cash Flow Hedging [Member]	'	'	'	'
Summary of Cash Flow Hedge Activity [Abstract]	'	'	'	'
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	-3,047	-4,795	227	-4,096
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-2,012	-15	-4,564	2,223
Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	'	'	'	'
Cash Flow Hedging [Member] | Interest Rate Swap [Member]	'	'	'	'
Summary of Cash Flow Hedge Activity [Abstract]	'	'	'	'
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	-907	-1,684	141	-4,697
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Interest Expense [Member]	'	'	'	'
Summary of Cash Flow Hedge Activity [Abstract]	'	'	'	'
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-1,844	-1,853	-5,460	-5,518
Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	'	'	'	'
Cash Flow Hedging [Member] | Commodity Contract [Member]	'	'	'	'
Summary of Cash Flow Hedge Activity [Abstract]	'	'	'	'
Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	-2,140	-3,111	86	601
Cash Flow Hedging [Member] | Commodity Contract [Member] | Revenue [Member]	'	'	'	'
Summary of Cash Flow Hedge Activity [Abstract]	'	'	'	'
Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	-168	1,838	896	7,741
Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	'	'	'	'
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Unrealized Gain Loss on Interest Rate Swaps [Member]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments [Abstract]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	3,144	605	29,393	-2,902
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Interest Expense [Member]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments [Abstract]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	-3,300	-3,250	-10,056	-9,697
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Revenue [Member]	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments [Abstract]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	'	($14)	'	($14)

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'
Cash and cash equivalents	$13,637		$15,462		$247,192
Restricted cash and equivalents	6,782		7,916		7,302
Notes payable	138,300		277,000		225,000
Carrying (Reported) Amount, Fair Value Disclosure [Member]	'		'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'
Cash and cash equivalents	13,637		15,462		247,192
Restricted cash and equivalents	6,782		7,916		7,302
Notes, Loans and Financing Receivable, Net, Current	0		0		21,832
Notes payable	138,300		277,000		225,000
Long-term Debt	1,211,673		1,042,850		1,271,260
Fair Value [Member]	'		'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'
Cash and Cash Equivalents, Fair Value	13,637	[1]	15,462	[1]	247,192	[1]
Restricted Cash, Fair Value	6,782	[1]	7,916	[1]	7,302	[1]
Notes Receivable, Fair Value Disclosure	0	[1]	0	[1]	21,832	[1]
Short-term Debt, Fair Value	138,300	[1]	277,000	[1]	225,000	[1]
Long-term Debt, Fair Value	$1,325,729	[2]	$1,231,559	[2]	$1,471,932	[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.

Commitments_and_Contingencies_

Commitments and Contingencies Commitments and Contingencies (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Electric Utilities [Member] | Loss from Catastrophes [Member]	'
Long-term Purchase Commitment [Line Items]	'
Loss Contingency, Damages Sought, Value	$8
Cheyenne Prairie [Member]	'
Long-term Purchase Commitment [Line Items]	'
Long-term Purchase Commitment, Amount	$222
Cheyenne Prairie [Member] | Equipment [Member]	'
Long-term Purchase Commitment [Line Items]	'
Long Term Purchase Commitment, Percentage Committed	94.00%
Cheyenne Prairie [Member] | Construction Contracts [Member]	'
Long-term Purchase Commitment [Line Items]	'
Long Term Purchase Commitment, Percentage Committed	67.00%
Basin Electric [Member]	'
Long-term Purchase Commitment [Line Items]	'
Number of Megawatts Capacity Purchased Under Long-term Contract	40
Long-term Contract for Purchase of Electric Power, Date of Contract Expiration	30-Sep-14

Commitments_and_Contingencies_1

Commitments and Contingencies Purchase and Sale Agreement (Details) (CTII Natural Gas-Fred Generating Unit [Member], Power Generation [Member], USD $)	0 Months Ended
In Millions, unless otherwise specified	6-May-13
CTII Natural Gas-Fred Generating Unit [Member] | Power Generation [Member]	'
Amount of Expected Consideration To Be Received Upon Closing of Sale	$22

Commitments_and_Contingencies_2

Commitments and Contingencies Supply Agreements (Details) (Basin Electric [Member])	9 Months Ended
	Sep. 30, 2013
	MW
Basin Electric [Member]	'
Supply Commitment [Line Items]	'
Number of Megawatts Sold Under Long-Term Contract	40
Long-term Contract To Sell Electric Power, Date of Contract Expiration	30-Sep-14

Commitments_and_Contingencies_3

Commitments and Contingencies Dividend Restrictions (Details) (USD $)	Sep. 30, 2013
Utilities Group [Member]	'
Related Party Transaction [Line Items]	'
Restricted Net Assets for Subsidiaries	$148,600,000
Non Regulated Energy Group [Member]	'
Related Party Transaction [Line Items]	'
Restricted Net Assets for Subsidiaries	$100,000,000

Commitments_and_Contingencies_4

Commitments and Contingencies Guarantees (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Mar. 29, 2013	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2013
				Electric Utilities [Member]	Electric Utilities [Member]	Gas Utilities [Member]	Gas Utilities [Member]	Letter of Credit [Member]
				Wind Turbines [Member]	Wind Turbines [Member]	Natural Gas Supplier Cross Timbers [Member]	Natural Gas Supplier Cross Timbers [Member]	Natural Gas Supplier Cross Timbers [Member]
								Gas Utilities [Member]
Guarantor Obligations [Line Items]	'	'	'	'	'	'	'	'
Guarantor Obligations, Maximum Exposure, Undiscounted	'	'	'	'	$33,300,000	'	$7,500,000	'
Guarantee Expiration Date	'	'	'	29-Mar-13	'	30-Jun-13	'	'
Letters of Credit Outstanding, Amount	$53,137,000	$36,300,000	$36,300,000	'	'	'	'	$5,000,000

Sale_of_Assets_Sales_of_Assets

Sale of Assets Sales of Assets (Details) (USD $)	9 Months Ended	0 Months Ended			3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 18, 2012	Sep. 27, 2012		Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2012
		Electric Utilities [Member]	Williston Basin Assets [Member]		Williston Basin Assets [Member]	Williston Basin Assets [Member]	Busch Ranch Wind Farm [Member]
			Oil and Gas [Member]		Oil and Gas [Member]	Oil and Gas [Member]	Electric Utilities [Member]
Disposal Date	27-Sep-12	'	'		'	'	'
Effective Date, Disposal	'	'	'		'	1-Jul-12	'
Gain (Loss) on Sale of Oil and Gas Property	'	'	'		'	$27,300,000	'
Proceeds from sale [Roll Forward]	'	'	'		'	'	'
Proceeds from Sale of Oil and Gas Property and Equipment (Beginning of Period)	'	'	243,314,000		227,860,000	'	'
Post Close Adjustment	'	'	'		-2,793,000	'	'
Transaction Costs, Disoposal	'	'	1,400,000		'	'	'
Back-in Contract Termination Fee	'	'	16,847,000	[1]	'	'	'
Proceeds from Sale of Oil and Gas Property and Equipment (End of Period)	'	'	243,314,000		227,860,000	'	'
Jointly Owned Utility Plant, Proportionate Ownership Share	'	'	'		'	'	50.00%
Proceeds from Sale of Property, Plant, and Equipment	'	$25,000,000	'		'	'	'
[1]	Required payment, triggered by the sale of the property, arising from a contractual obligation contained in the original participation agreement with the property operator.

Recovered_Sheet1

Impairment of Long-Lived Assets(Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2012
					Oil and Gas Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]	'	'	'	'	'
Impairment of long-lived asets	$0	$0	$0	$26,868	'
Natural Gas Price Per MCF, NYMEX	'	'	'	'	3.15
Average Natural Gas Price Per MCF, Wellhead	'	'	'	'	2.66
Crude Oil Price, per Barrel, NYMEX	'	'	'	'	95.67
Crude Oil Price Per Barrel, Wellhead	'	'	'	'	85.36

Part_II_Item_5_Fair_Value_Meas2

Part II, Item 5 - Fair Value Measurements Fair Value Balance Sheet Offsetting (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	$4,156	$5,332	$1,490	$11,623
Gross Amounts Offset In Statement Of Financial Position Assets	-4,030	-1,586	15,740	8,931
Derivative Assets	126	3,746	17,230	20,554
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	95,581	131,010	131,229	143,887
Gross Amounts Offset In Statement Of Financial Position Liabilities	-18,249	-17,528	-3,310	-10,487
Derivative Liabilities	77,332	113,482	127,919	133,400
Contract Subject To Master Netting Arrangement [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	4,030	1,970	-2,432	965
Gross Amounts Offset In Statement Of Financial Position Assets	-4,030	-1,586	15,740	8,931
Derivative Assets	0	384	13,308	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	12,289	11,568	4,527	17,643
Gross Amounts Offset In Statement Of Financial Position Liabilities	-12,289	-11,568	0	-10,487
Derivative Liabilities	0	0	4,527	7,156
Contract Subject To Master Netting Arrangement [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	2,351	1,629	-2,726	965
Gross Amounts Offset In Statement Of Financial Position Assets	-2,351	-1,586	15,740	8,931
Derivative Assets	0	43	13,014	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	10,747	10,162	4,527	17,643
Gross Amounts Offset In Statement Of Financial Position Liabilities	-10,747	-10,162	0	-10,487
Derivative Liabilities	0	0	4,527	7,156
Contract Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	40	76	95	'
Gross Amounts Offset In Statement Of Financial Position Assets	-40	0	0	'
Derivative Assets	0	76	95	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	1,284	449	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-1,284	-449	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Natural Gas [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	1,639	172	5	'
Gross Amounts Offset In Statement Of Financial Position Assets	-1,639	0	0	'
Derivative Assets	0	172	5	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	181	620	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-181	-620	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Commodity Option [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	93	194	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	0	93	194	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	77	337	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	-77	-337	0	'
Derivative Liabilities	0	0	0	'
Contract Subject To Master Netting Arrangement [Member] | Interest Rate Swap [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	0	0	0	'
Contract Not Subject To Master Netting Arrangement [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	126	3,362	3,922	10,658
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	126	3,362	3,922	10,658
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	83,292	119,442	126,702	126,244
Gross Amounts Offset In Statement Of Financial Position Liabilities	-5,960	-5,960	-3,310	0
Derivative Liabilities	77,332	113,482	123,392	126,244
Contract Not Subject To Master Netting Arrangement [Member] | Purchase Contract [Member] | Natural Gas, Distribution [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	0	0	0	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	0	0	0	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	0	0	0	'
Contract Not Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	11	1,249	1,431	1,500
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	11	1,249	1,431	1,500
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	34	52	56	'
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	'
Derivative Liabilities	34	52	56	'
Contract Not Subject To Master Netting Arrangement [Member] | Basis Swap [Member] | Natural Gas [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	113	1,828	2,066	9,158
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	0
Derivative Assets	113	1,828	2,066	9,158
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	51	507	1,181	7
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	0
Derivative Liabilities	51	507	1,181	7
Contract Not Subject To Master Netting Arrangement [Member] | Commodity Option [Member] | Crude Oil [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	2	285	425	'
Gross Amounts Offset In Statement Of Financial Position Assets	0	0	0	'
Derivative Assets	2	285	425	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	65	795	885	3,370
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0	0	0
Derivative Liabilities	65	795	885	3,370
Contract Not Subject To Master Netting Arrangement [Member] | Interest Rate Swap [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liability, Fair Value, Gross Liability	83,142	118,088	124,580	122,867
Gross Amounts Offset In Statement Of Financial Position Liabilities	-5,960	-5,960	-3,310	0
Derivative Liabilities	$77,182	$112,128	$121,270	$122,867

Part_II_Item_5_Fair_Value_Meas3

Part II, Item 5 - Fair Value Measurements Fair Value Balance Sheet Offsetting by Counterparty (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	$126	$3,746	$17,230	$20,554
Derivative, Collateral, Obligation to Return Cash	0	0	-2,414	0
Net Amount with Counterparty, after cash collateral and netting	126	3,746	14,816	20,554
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	77,332	113,482	127,919	133,400
Derivative, Collateral, Right to Reclaim Cash	-3,688	-6,141	0	0
Net Amount with Counterparty, after collateral and netting	73,644	107,341	127,919	133,400
Counterparty D [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	3,563	4,588	4,903	5,140
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	3,563	4,588	4,903	5,140
Counterparty E [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	19,993	29,245	31,147	31,095
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	19,993	29,245	31,147	31,095
Counterparty F [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	9,858	12,721	13,554	13,880
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	9,858	12,721	13,554	13,880
Counterparty G [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	20,138	26,520	27,610	26,329
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	20,138	26,520	27,610	26,329
Counterparty H [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	8,857	16,809	20,331	23,203
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	8,857	16,809	20,331	23,203
Counteryparty I [Member]	'	'	'	'
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	14,773	22,245	23,725	23,220
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	14,773	22,245	23,725	23,220
Utilities Group [Member] | Counterparty A [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	0	43	13,014	9,896
Derivative, Collateral, Obligation to Return Cash	0	0	0	0
Net Amount with Counterparty, after cash collateral and netting	0	43	13,014	9,896
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	0	0	4,527	7,156
Derivative, Collateral, Right to Reclaim Cash	-3,333	-4,354	0	0
Net Amount with Counterparty, after collateral and netting	-3,333	-4,354	4,527	7,156
Oil and Gas [Member] | Counterparty A [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	0	341	294	0
Derivative, Collateral, Obligation to Return Cash	0	0	-2,414	0
Net Amount with Counterparty, after cash collateral and netting	0	341	-2,120	0
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	0	0	0	0
Derivative, Collateral, Right to Reclaim Cash	-355	-1,787	0	0
Net Amount with Counterparty, after collateral and netting	-355	-1,787	0	0
Oil and Gas [Member] | Counterparty B [Member]	'	'	'	'
Derivative Assets [Abstract]	'	'	'	'
Derivative Assets	126	3,362	3,922	10,658
Derivative, Collateral, Obligation to Return Cash	0	0	0	0
Net Amount with Counterparty, after cash collateral and netting	126	3,362	3,922	10,658
Derivative Liabilities [Abstract]	'	'	'	'
Derivative Liabilities	150	1,354	2,122	3,377
Derivative, Collateral, Right to Reclaim Cash	0	0	0	0
Net Amount with Counterparty, after collateral and netting	$150	$1,354	$2,122	$3,377