Black Hills (BKH) 10-Q 4 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2015	Oct. 31, 2015
Document Information [Line Items]
Entity Registrant Name	BLACK HILLS CORP /SD/
Entity Central Index Key	1,130,464
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
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		44,850,752
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Loss) (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenue	$ 272,105	$ 272,087	$ 986,346	$ 1,015,493
Utilities -
Fuel, purchased power and cost of natural gas sold	71,627	84,674	350,778	416,473
Operations and maintenance	67,282	64,245	205,630	201,546
Non-regulated energy operations and maintenance	22,548	20,170	67,744	63,852
Depreciation, depletion and amortization	37,768	36,628	116,821	107,754
Taxes - property, production and severance	10,675	11,082	33,988	32,462
Impairment of long-lived assets	61,875	0	178,395	0
Other operating expenses	2,374	49	3,392	323
Total operating expenses	274,149	216,848	956,748	822,410
Operating income (loss)	(2,044)	55,239	29,598	193,083
Interest charges -
Interest expense incurred (including amortization of debt issuance costs, premiums and discounts and realized settlements on interest rate swaps)	(22,378)	(17,919)	(61,833)	(53,665)
Allowance for funds used during construction - borrowed	478	319	843	845
Capitalized interest	280	231	1,037	734
Interest income	414	575	1,163	1,541
Allowance for funds used during construction - equity	430	297	563	828
Other income (expense), net	842	261	1,568	1,262
Total other income (expense), net	(19,934)	(16,236)	(56,659)	(48,455)
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	(21,978)	39,003	(27,061)	144,628
Equity in earnings (loss) of unconsolidated subsidiaries	0	0	(344)	(1)
Impairment of equity investments	0	0	(5,170)	0
Income tax benefit (expense)	12,035	(11,640)	14,640	(48,272)
Net income (loss) available for common stock	$ (9,943)	$ 27,363	$ (17,935)	$ 96,355
Earnings (loss) per share of common stock:
Total income (loss) per share, Basic	$ (0.22)	$ 0.62	$ (0.40)	$ 2.17
Total income (loss) per share, Diluted	$ (0.22)	$ 0.61	$ (0.40)	$ 2.16
Weighted average common shares outstanding:
Basic	44,635	44,415	44,598	44,382
Diluted	44,635	44,608	44,598	44,584
Dividends declared per share of common stock	$ 0.405	$ 0.390	$ 1.215	$ 1.170

Condensed Consolidated Stateme3

Condensed Consolidated Statement of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss) available for common stock	$ (9,943)	$ 27,363	$ (17,935)	$ 96,355
Other comprehensive income (loss), net of tax:
Fair value adjustments on derivatives designated as cash flow hedges (net of tax (expense) benefit of $(1,609) and $(1,840) for the three months ended 2015 and 2014 and $(1,482) and $582 for the nine months ended 2015 and 2014, respectively)	2,773	3,145	2,644	(1,071)
Reclassification adjustments for cash flow hedges settled and included in net income (loss) (net of tax (expense) benefit of $558 and $(732) for the three months ended 2015 and 2014 and $2,548 and $(1,931) for the nine months ended 2015 and 2014, respectively)	(948)	1,328	(3,450)	3,511
Benefit plan liability adjustments - net gain (loss) (net of tax (expense) benefit of $0 and $0 for the three months ended 2015 and 2014 and $16 and $2 for the nine months ended 2015 and 2014, respectively)	0	0	(27)	(2)
Benefit plan liability tax adjustments - net gain (loss)	0	0	0	(394)
Benefit plan liability adjustments - prior service cost (net of tax (expense) benefit of $0 and $0 for the three months ended 2015 and 2014 and $0 and $(90) for the nine months ended 2015 and 2014, respectively)	0	0	0	164
Reclassification adjustments of benefit plan liability - prior service cost (net of tax (expense) benefit of $19 and $17 for the three months ended 2015 and 2014 and $58 and $60 for the nine months ended 2015 and 2014, respectively)	(36)	(31)	(108)	(110)
Reclassification adjustments of benefit plan liability - net gain (loss) (net of tax (expense) benefit of $(247) and $(86) for the three months ended 2015 and 2014 and $(742) and $(262) for the nine months ended 2015 and 2014, respectively)	459	160	1,374	485
Other comprehensive income (loss), net of tax	2,248	4,602	433	2,583
Comprehensive income (loss) available for common stock	$ (7,695)	$ 31,965	$ (17,502)	$ 98,938

Condensed Consolidated Stateme4

Condensed Consolidated Statement of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Fair value adjustment on derivatives designated as cash flow hedges, (tax) benefit	$ (1,609)	$ (1,840)	$ (1,482)	$ 582
Reclassification adjustments of cash flow hedges settled and included in net income, (tax) benefit	558	(732)	2,548	(1,931)
Benefit plan liability adjustments net gain, (tax) benefit	0	0	16	2
Benefit plan liability adjustments prior service cost, (tax) benefit	0	0	0	(90)
Reclassification adjustment of benefit plan prior service cost included in net income, (tax) benefit	19	17	58	60
Reclassification adjustment of benefit plan liabilities actuarial gain (loss), (tax) benefit	$ (247)	$ (86)	$ (742)	$ (262)

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Current assets:
Cash and cash equivalents	$ 38,841	$ 21,218	$ 11,939
Restricted cash and equivalents	2,462	2,056	1,918
Accounts receivable, net	115,502	189,992	123,399
Materials, supplies and fuel	90,349	91,191	105,726
Derivative assets, current	0	0	0
Income tax receivable, net	0	2,053	1,268
Deferred income tax assets, net, current	47,783	48,288	34,756
Regulatory assets, current	51,962	74,396	68,444
Other current assets	55,383	24,842	26,502
Total current assets	402,282	454,036	373,952
Investments	12,148	17,294	17,144
Property, plant and equipment	4,882,420	4,563,400	4,493,696
Less: accumulated depreciation and depletion	(1,617,723)	(1,357,929)	(1,373,247)
Total property, plant and equipment, net	3,264,697	3,205,471	3,120,449
Other assets:
Goodwill	359,527	353,396	353,396
Intangible assets, net	3,440	3,176	3,231
Regulatory assets, non-current	182,337	183,443	140,422
Derivative assets, non-current	0	0	0
Other assets, non-current	22,131	29,086	29,930
Total other assets, non-current	567,435	569,101	526,979
TOTAL ASSETS	4,246,562	4,245,902	4,038,524
Current liabilities:
Accounts payable	91,633	124,139	100,444
Accrued liabilities	229,957	170,115	163,374
Derivative liabilities, current	3,312	3,340	3,397
Accrued Income Taxes	308	0	0
Regulatory liabilities, current	5,647	3,687	828
Notes payable	117,900	75,000	184,000
Current maturities of long-term debt	0	275,000	275,000
Total current liabilities	448,757	651,281	727,043
Long-term debt, net of current maturities	1,567,797	1,267,589	1,107,519
Deferred credits and other liabilities:
Deferred income tax liabilities, net, non-current	494,834	511,952	494,095
Derivative liabilities, non-current	722	2,680	3,273
Regulatory liabilities, non-current	152,164	145,144	118,856
Benefit plan liabilities	158,614	158,966	108,924
Other deferred credits and other liabilities	136,462	154,406	144,089
Total deferred credits and other liabilities	$ 942,796	$ 973,148	$ 869,237
Commitments and contingencies (See Notes 2, 9, 10, 15, 16)
Stockholders’ equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 44,891,626; 44,714,072; and 44,696,670 shares, respectively	$ 44,892	$ 44,714	$ 44,697
Additional Paid in Capital	753,856	748,840	746,575
Retained earnings	504,864	577,249	560,133
Treasury stock, at cost – 36,711; 42,226; and 41,552 shares, respectively	(1,789)	(1,875)	(1,841)
Accumulated other comprehensive income (loss)	(14,611)	(15,044)	(14,839)
Total stockholders’ equity	1,287,212	1,353,884	1,334,725
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 4,246,562	$ 4,245,902	$ 4,038,524

Condensed Consolidated Balance6

Condensed Consolidated Balance Sheets (unaudited) Condensed Consolidated Balance Sheets (Parentheticals) - $ / shares	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Statement of Financial Position [Abstract]
Common Stock, Par Per Share	$ 1	$ 1	$ 1
Common Stock, Shares Issued	44,891,626	44,714,072	44,696,670
Treasury Stock, Shares	36,711	42,226	41,552
Common Stock, Shares Authorized	100,000,000	100,000,000	100,000,000

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net income (loss) available for common stock	$ (17,935)	$ 96,355
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	116,821	107,754
Deferred financing cost amortization	3,074	1,608
Impairment of long-lived assets	183,565	0
Derivative fair value adjustments	(8,851)	2,136
Stock compensation	2,868	6,978
Deferred income taxes	(20,808)	48,930
Employee benefit plans	15,175	11,109
Other adjustments, net	4,013	2,016
Changes in certain operating assets and liabilities:
Materials, supplies and fuel	3,618	(17,248)
Accounts receivable, unbilled revenues and other operating assets	75,966	53,511
Accounts payable and other operating liabilities	(5,255)	(14,307)
Regulatory assets - current	27,768	(43,727)
Regulatory liabilities - current	2,457	(9,845)
Contributions to defined benefit pension plans	(10,200)	(10,200)
Other operating activities, net	(6,403)	4,087
Net cash provided by (used in) operating activities	365,873	239,157
Investing activities:
Property, plant and equipment additions	(349,471)	(290,299)
Proceeds from sale of assets	0	22,342
Other investing activities	(7,189)	(2,364)
Net cash provided by (used in) investing activities	(356,660)	(270,321)
Financing activities:
Dividends paid on common stock	(54,450)	(52,218)
Common stock issued	2,484	2,393
Short-term borrowings - issuances	287,910	396,250
Short-term borrowings - repayments	(245,010)	(294,750)
Long-term debt - issuances	300,000	0
Long-term debt - repayments	(275,000)	(12,200)
Other financing activities	(7,524)	(4,213)
Net cash provided by (used in) financing activities	8,410	35,262
Net change in cash and cash equivalents	17,623	4,098
Cash and Cash Equivalents
Cash and cash equivalents, beginning of period	21,218	7,841
Cash and cash equivalents, end of period	$ 38,841	$ 11,939

Management's Statement_

Management's Statement:	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Statement	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 2014 Annual Report on Form 10-K/A 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 September 30, 2015 , December 31, 2014 , and September 30, 2014 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 prices. 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 September 30, 2015 and September 30, 2014 , and our financial condition as of September 30, 2015 , December 31, 2014 , and September 30, 2014 , are not necessarily indicative of the results of operations and financial condition to be expected as of or for any other period. All earnings per share amounts discussed refer to diluted earnings per share unless otherwise noted. Recently Issued and Adopted Accounting Standards We have implemented all new accounting pronouncements that are in effect and may impact our financial statements. We are currently assessing the impact any other new accounting pronouncements that have been issued may have on our financial position, results of operations, or cash flows. Simplifying the Presentation of Debt Issuance Costs, ASU 2015-03 In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs. Debt issuance costs related to a recognized debt liability will be presented on the balance sheet as a direct deduction from the debt liability, similar to the presentation of debt discounts, rather than as an asset. Amortization of these costs will continue to be reported as interest expense. ASU 2015-03 is effective for annual and interim reporting periods beginning after December 15, 2015. Early adoption is permitted. We are currently evaluating the impact of adoption that ASU 2015-03 will have on our financial position, results of operations or cash flows. Revenue from Contracts with Customers, ASU 2014-09 In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. On July 9, 2015, FASB voted to defer the effective date of ASU 2014-09 by one year. The guidance would be effective for annual and interim reporting periods beginning after December 15, 2018 and early adoption is permitted. We are currently assessing the impact that adoption of ASU 2014-09 will have on our financial position, results of operations or cash flows. Correction of Immaterial Errors In preparing our condensed consolidated financial statements for the quarter ended June 30, 2015, we identified immaterial errors that impacted our previously issued consolidated financial statements. The prior period errors originated in the year ended December 31, 2008 and related to our oil and gas full cost ceiling impairment calculation to determine whether the net book value of our oil and gas properties exceeded the ceiling. Specifically, the errors related to evaluating and correctly accounting for the treatment of tax-related amounts associated with the calculation. The errors identified caused an understatement of 2008, 2009, 2012 and Q1 2015 non-cash ceiling test impairment calculations, which resulted in an overstatement of depletion expense from 2009 through March 31, 2015, and an understatement of the 2012 gain on sale of oil and gas properties. In accordance with Staff Accounting Bulletin (SAB) No. 99, Materiality , and SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements , we evaluated these errors, including both qualitative and quantitative considerations, and concluded that the errors did not, individually or in the aggregate, result in a material misstatement of our previously issued condensed consolidated financial statements. The following tables present the revisions to particular line items resulting from the corrections of these errors in this Quarterly Report on Form 10-Q. The impact of the errors relate entirely to our Oil and Gas segment. CONDENSED CONSOLIDATED STATEMENTS OF INCOME For the Three Months Ended September 30, 2014 For the Nine Months Ended September 30, 2014 As Reported Adjustments As Revised As Reported Adjustments As Revised (in thousands, expect per share amounts) Depreciation, depletion and amortization $ 37,463 $ (835 ) $ 36,628 $ 110,258 $ (2,504 ) $ 107,754 Total operating expenses $ 217,683 $ (835 ) $ 216,848 $ 824,914 $ (2,504 ) $ 822,410 Operating income (loss) $ 54,404 $ 835 $ 55,239 $ 190,579 $ 2,504 $ 193,083 Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes $ 38,168 $ 835 $ 39,003 $ 142,124 $ 2,504 $ 144,628 Income tax benefit (expense) $ (11,332 ) $ (308 ) $ (11,640 ) $ (47,349 ) $ (923 ) $ (48,272 ) Net income (loss) available for common stock $ 26,836 $ 527 $ 27,363 $ 94,774 $ 1,581 $ 96,355 Earnings (loss) per share of common stock: Earnings (loss) per share, Basic $ 0.60 $ 0.02 $ 0.62 $ 2.14 $ 0.03 $ 2.17 Earnings (loss) per share, Diluted $ 0.60 $ 0.01 $ 0.61 $ 2.13 $ 0.03 $ 2.16 CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) For the Three Months Ended September 30, 2014 For the Nine Months Ended September 30, 2014 (in thousands) As Reported Adjustments As Revised As Reported Adjustments As Revised Net income (loss) available for common stock $ 26,836 $ 527 $ 27,363 $ 94,774 $ 1,581 $ 96,355 Comprehensive income (loss) $ 31,438 $ 527 $ 31,965 $ 97,357 $ 1,581 $ 98,938 CONDENSED CONSOLIDATED BALANCE SHEETS As of September 30, 2014 As Reported Adjustments As Revised (in thousands) Accumulated depreciation and depletion $ (1,338,509 ) $ (34,738 ) $ (1,373,247 ) Total property, plant and equipment, net $ 3,155,187 $ (34,738 ) $ 3,120,449 TOTAL ASSETS $ 4,073,262 $ (34,738 ) $ 4,038,524 Deferred income tax liability, non-current $ 506,166 $ (12,071 ) $ 494,095 Total deferred credits and other liabilities $ 881,308 $ (12,071 ) $ 869,237 Retained earnings $ 582,800 $ (22,667 ) $ 560,133 Total stockholders' equity $ 1,357,392 $ (22,667 ) $ 1,334,725 TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY $ 4,073,262 $ (34,738 ) $ 4,038,524 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Nine Months Ended September 30, 2014 As Reported Adjustments As Revised (in thousands) Net income (loss) available for common stock $ 94,774 $ 1,581 $ 96,355 Adjustments to reconcile net income (loss) to net cash provided by operating activities: Depreciation, depletion and amortization $ 110,258 $ (2,504 ) $ 107,754 Deferred income taxes $ 48,007 $ 923 $ 48,930 Net cash provided by (used in) operating activities $ 239,157 $ — $ 239,157 The Notes to the Condensed Consolidated Financial Statements have been revised to reflect the correction of these errors for all periods presented.

Acquisition_

Acquisition:	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Acquisition	ACQUISITION Acquisition of SourceGas On July 12, 2015, Black Hills Utility Holdings entered into a definitive agreement to acquire SourceGas Holdings LLC and its subsidiaries from investment funds managed by Alinda Capital Partners and GE Energy Financial Services, a unit of General Electric Co. (NYSE:GE), for approximately $1.89 billion , which includes $200 million of projected capital expenditures through closing and the assumption of $700 million in debt projected at closing. The effective purchase price is estimated to be $1.74 billion after taking into account approximately $150 million of future tax benefits associated with acquired NOLs and the step up in certain assets including goodwill resulting from the transaction. The purchase price is subject to customary post-closing adjustments for cash, capital expenditures, indebtedness and working capital. In conjunction with the agreement, we entered into a commitment letter for a one-year, $1.17 billion senior unsecured fully-committed bridge facility provided by Credit Suisse, subsequently replaced on August 6, 2015 by the Bridge Term Loan Agreement discussed below. We expect to finance the acquisition with equity proceeds of $450 million to $600 million , including $200 million to $300 million of unit mandatory convertibles, $450 million to $550 million of new long-term indebtedness, and assuming approximately $700 million of continuing debt of SourceGas, with the remainder funded from cash on hand and draws under our revolving credit agreement. SourceGas primarily operates four regulated natural gas utilities serving approximately 425,000 customers in Arkansas, Colorado, Nebraska and Wyoming and a 512 mile regulated intrastate natural gas transmission pipeline in Colorado. Following completion of the transaction, SourceGas will be a wholly-owned subsidiary of Black Hills Utility Holdings. The agreement for the acquisition of SourceGas is subject to various provisions including representations, warranties, and covenants with respect to Arkansas, Colorado, Nebraska and Wyoming utility businesses that are subject to customary conditions and limitations. Completion of the transaction is also subject to regulatory approvals from the APSC, CPUC, NPSC and WPSC, and was also subject to notification, clearance and reporting requirements under the Hart-Scott-Rodino Act, which waiting period expired on August 18, 2015. On August 10, 2015, we filed joint applications with the APSC, CPUC, NPSC and WPSC, requesting a March 1, 2016 approval date in all four filings. The discovery process with all four state commissions is ongoing and the acquisition is expected to close during the first half of 2016. BHC has guaranteed the full and complete payment and performance of Black Hills Utility Holdings. Effective August 6, 2015, we entered into a Bridge Term Loan Agreement with Credit Suisse as the Administrative Agent and 10 additional banks, collectively, for commitments totaling $1.17 billion pursuant to the previously executed bridge commitment letter with Credit Suisse. We may draw up to $1.17 billion on this loan to fund the SourceGas Acquisition and related expenses. The Agreement contains the same customary affirmative and negative covenants as contained in our Revolving Credit Agreement and Term Loan Credit Agreement, such as limitations on the creation of new indebtedness and on certain liens, restrictions on certain transactions and maintaining a recourse leverage ratio not to exceed 0.75 to 1 . In the event we fund under the Bridge Term Loan Agreement, in certain circumstances, we are required to pay down those borrowings with funds received from the proceeds of equity and debt offerings and asset sales. Additionally, our Revolving Credit Facility and Term Loan Credit Agreements were amended in connection with the Bridge Term Loan Agreement to permit the assumption of certain indebtedness of SourceGas and to increase the Recourse Leverage Ratio in certain circumstances. In these amendments, the maximum Recourse Ratio is no greater than 0.65 to 1 at the end of any fiscal quarter, but may increase to (i) 0.70 to 1 at the end of any fiscal quarter during such four fiscal quarter period where the aggregate outstanding debt assumed or incurred in connection with our acquisition of SourceGas is equal to or greater than $1.25 billion and less than $1.46 billion or (ii) 0.75 to 1 at the end of any fiscal quarter during such four fiscal quarter period that the aggregate outstanding debt assumed or incurred in connection with our acquisition of SourceGas is equal to or greater than $1.46 billion .

Business Segment Information_

Business Segment Information:	9 Months Ended
	Sep. 30, 2015
Segment Reporting Information, Additional Information [Abstract]
Business Segment Information	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 September 30, 2015 External Operating Revenue Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 182,263 $ 2,547 $ 21,982 Gas 68,934 — 1,630 Non-regulated Energy: Power Generation 2,123 21,128 9,067 Coal Mining 8,890 8,076 3,047 Oil and Gas (a) 9,895 — (39,769 ) Corporate activities (c) — — (5,900 ) Inter-company eliminations — (31,751 ) — Total $ 272,105 $ — $ (9,943 ) Three Months Ended September 30, 2014 External Operating Revenue Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 171,395 $ 3,156 $ 18,154 Gas 78,735 — 1,597 Non-regulated Energy: Power Generation 1,602 20,419 7,829 Coal Mining 6,884 8,689 2,638 Oil and Gas 13,471 — (2,583 ) Corporate activities — — (272 ) Inter-company eliminations — (32,264 ) — Total $ 272,087 $ — $ 27,363 Nine Months Ended September 30, 2015 External Operating Revenues Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 534,988 $ 8,480 $ 58,613 Gas 386,011 — 27,007 Non-regulated Energy: Power Generation 5,782 62,452 24,761 Coal Mining 26,084 23,541 9,106 Oil and Gas (a)(b) 33,481 — (130,079 ) Corporate activities (c) — — (7,343 ) Inter-company eliminations — (94,473 ) — Total $ 986,346 $ — $ (17,935 ) Nine Months Ended September 30, 2014 External Operating Revenues Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 508,230 $ 10,307 $ 44,156 Gas 440,571 — 28,289 Non-regulated Energy: Power Generation 4,138 62,211 23,096 Coal Mining 19,085 26,637 7,118 Oil and Gas 43,469 — (5,211 ) Corporate activities — — (1,093 ) Inter-company eliminations — (99,155 ) — Total $ 1,015,493 $ — $ 96,355 __________ (a) Net income (loss) for the three and nine months ended September 30, 2015 included non-cash after-tax ceiling test impairments of $36 million and $113 million , respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (b) Net income (loss) for the nine months ended September 30, 2015 included a non-cash after-tax impairment to equity investments of $3.4 million . See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (c) Net income (loss) for the three and nine months ended September 30, 2015 included incremental, non-recurring acquisition costs, net of tax of $2.8 million and $3.0 million , respectively and after-tax internal labor costs attributable to the acquisition of $1.2 million and $1.8 million , respectively. See Note 2 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. 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: September 30, 2015 December 31, 2014 September 30, 2014 Utilities: Electric (a) $ 2,846,931 $ 2,748,680 $ 2,671,601 Gas 831,802 906,922 827,069 Non-regulated Energy: Power Generation (a) 78,666 76,945 64,359 Coal Mining 78,000 74,407 74,130 Oil and Gas (b) (c) 280,842 332,343 296,043 Corporate activities 130,321 106,605 105,322 Total assets $ 4,246,562 $ 4,245,902 $ 4,038,524 __________ (a) The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under accounting for a capital lease. (b) As a result of continued low commodity prices during 2015, we recorded non-cash impairments of oil and gas assets included in our Oil and Gas segment of $62 million and $178 million for the for the three and nine months ended September 30, 2015 , respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (c) Includes a non-cash impairment of our Oil and Gas equity investments of $5.2 million for the nine months ended September 30, 2015 . See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.

Accounts Receivable_

Accounts Receivable:	9 Months Ended
	Sep. 30, 2015
Receivables [Abstract]
Accounts Receivable	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 September 30, 2015 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 43,337 $ 35,069 $ (720 ) $ 77,686 Gas Utilities 18,349 10,140 (618 ) 27,871 Power Generation 1,186 — — 1,186 Coal Mining 2,684 — — 2,684 Oil and Gas 4,522 — (13 ) 4,509 Corporate 1,566 — — 1,566 Total $ 71,644 $ 45,209 $ (1,351 ) $ 115,502 Accounts Unbilled Less Allowance for Accounts December 31, 2014 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 59,714 $ 26,474 $ (722 ) $ 85,466 Gas Utilities 47,394 45,546 (781 ) 92,159 Power Generation 1,369 — — 1,369 Coal Mining 3,151 — — 3,151 Oil and Gas 5,305 — (13 ) 5,292 Corporate 2,555 — — 2,555 Total $ 119,488 $ 72,020 $ (1,516 ) $ 189,992 Accounts Unbilled Less Allowance for Accounts September 30, 2014 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 53,717 $ 21,485 $ (724 ) $ 74,478 Gas Utilities 23,409 13,218 (740 ) 35,887 Power Generation 1,368 — — 1,368 Coal Mining 2,563 — — 2,563 Oil and Gas 7,657 — (13 ) 7,644 Corporate 1,459 — — 1,459 Total $ 90,173 $ 34,703 $ (1,477 ) $ 123,399

Regulatory Accounting_

Regulatory Accounting:	9 Months Ended
	Sep. 30, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Accounting	REGULATORY ACCOUNTING We had the following regulatory assets and liabilities (in thousands): Maximum As of As of As of Amortization (in years) September 30, 2015 December 31, 2014 September 30, 2014 Regulatory assets Deferred energy and fuel cost adjustments - current (a) (d) 1 $ 25,354 $ 23,820 $ 26,211 Deferred gas cost adjustments (a)(d) 2 9,358 37,471 42,400 Gas price derivatives (a) 7 23,681 18,740 7,470 AFUDC (b) 45 12,580 12,358 12,411 Employee benefit plans (c) (e) 12 95,779 97,126 64,908 Environmental (a) subject to approval 1,209 1,314 1,314 Asset retirement obligations (a) 44 675 3,287 3,282 Bond issue cost (a) 23 3,169 3,276 3,311 Renewable energy standard adjustment (b) 5 5,102 9,622 12,007 Flow through accounting (c) 35 28,585 25,887 25,157 Decommissioning costs (f) 10 16,353 12,484 — Other regulatory assets (a) 15 12,454 12,454 10,395 $ 234,299 $ 257,839 $ 208,866 Regulatory liabilities Deferred energy and gas costs (a) (d) 1 $ 9,899 $ 6,496 $ 5,535 Employee benefit plans (c) (e) 12 53,140 53,139 34,409 Cost of removal (a) 44 86,946 78,249 71,362 Other regulatory liabilities (c) 25 7,826 10,947 8,378 $ 157,811 $ 148,831 $ 119,684 __________ (a) Recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively. (d) Our deferred energy, fuel cost, and gas cost adjustments represent the cost of electricity and gas delivered to our electric and gas utility customers that is either higher or lower than current rates and will be recovered or refunded in future rates. Fluctuations in deferred gas cost adjustments compared to the same period in the prior year are primarily due to higher natural gas prices driven by demand and market conditions from the peak winter heating season in the first part of 2014. Our electric and gas utilities file periodic quarterly, semi-annual, and/or annual filings to recover these costs based on the respective cost mechanisms approved by their applicable state utility commissions. (e) Increase compared to September 30, 2014 was driven by a decrease in the discount rate and a change in the mortality tables used in employee benefit plan estimates. (f) Black Hills Power has approximately $13 million of decommissioning costs associated with the retirements of the Neil Simpson I and Ben French power plants that are allowed a rate of return, in addition to recovery of costs.

Materials, Supplies and Fuel_

Materials, Supplies and Fuel:	9 Months Ended
	Sep. 30, 2015
Inventory, Net [Abstract]
Materials, Supplies and Fuel	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: September 30, 2015 December 31, 2014 September 30, 2014 Materials and supplies $ 53,838 $ 49,555 $ 52,682 Fuel - Electric Utilities 6,139 6,637 7,108 Natural gas in storage held for distribution 30,372 34,999 45,936 Total materials, supplies and fuel $ 90,349 $ 91,191 $ 105,726

Goodwill_

Goodwill:	9 Months Ended
	Sep. 30, 2015
Goodwill [Abstract]
Goodwill	GOODWILL Following is a summary of Goodwill included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: Electric Utilities Gas Utilities Power Generation Total Ending balance at December 31, 2014 $ 250,487 $ 94,144 $ 8,765 $ 353,396 Additions (a) 6,131 — — 6,131 Ending balance at September 30, 2015 $ 256,618 $ 94,144 $ 8,765 $ 359,527 __________ (a) Goodwill was recorded on the acquisition of Wyoming natural gas utility Energy West Wyoming, Inc., and natural gas pipeline assets from Energy West Development, Inc. completed on July 1, 2015.

Earnings Per Share_

Earnings Per Share:	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE A reconciliation of share amounts used to compute Earnings (loss) per share in the accompanying Condensed Consolidated Statements of Income (Loss) was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net income (loss) available for common stock $ (9,943 ) $ 27,363 $ (17,935 ) $ 96,355 Weighted average shares - basic 44,635 44,415 44,598 44,382 Dilutive effect of: Equity compensation — 193 — 202 Weighted average shares - diluted 44,635 44,608 44,598 44,584 Due to our net loss for the three and nine months ended September 30, 2015 , potentially dilutive securities were excluded from the diluted loss per share calculation due to their anti-dilutive effect. In computing diluted net loss per share, 58,380 and 82,130 equity compensation shares were excluded from the computations for the three and nine months ended September 30, 2015 , respectively. In addition to these potentially dilutive shares excluded due to our net loss for the three and nine months ended September 30, 2015 , the following outstanding securities were also excluded in the computation of diluted net income (loss) per share as their inclusion would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Equity compensation 121 99 114 75 Anti-dilutive shares 121 99 114 75

Notes Payable and Long-term Deb

Notes Payable and Long-term Debt:	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Notes Payable and Long-term debt	NOTES PAYABLE AND LONG-TERM DEBT We had the following short-term debt outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 Balance Outstanding Letters of Credit Balance Outstanding Letters of Credit Balance Outstanding Letters of Credit Revolving Credit Facility $ 117,900 $ 30,600 $ 75,000 $ 35,000 $ 184,000 $ 31,726 Revolving Credit Facility On June 26, 2015, we amended our $500 million corporate Revolving Credit Facility agreement to extend the term through June 26, 2020 . This facility is similar to the former agreement, which includes an accordion feature that allows us, with the consent of the administrative agent and issuing agents, to increase the capacity of the facility to $750 million . Borrowings continue to be available under a base rate or various Eurodollar rate options. The interest costs associated with the letters of credit or borrowings and the commitment fee under the Revolving Credit Facility are determined based upon our most favorable Corporate credit rating from S&P and Moody’s for our unsecured debt. Based on our credit ratings, the margins for base rate borrowings, Eurodollar borrowings, and letters of credit were 0.125% , 1.125% , and 1.125% , respectively, at September 30, 2015 . A commitment fee is charged on the unused amount of the Revolving Credit Facility and was 0.175% based on our credit rating. Replacement of Corporate Term Loan On April 13, 2015, we entered into a new $300 million Corporate term loan expiring April 12, 2017 . This new term loan replaced the $275 million Corporate term loan due on June 19, 2015 and was classified as Long-Term Debt as of September 30, 2015 . The additional $25 million , less interest and fees, was used for general corporate purposes. The cost of the borrowing under the new term loan is LIBOR plus a margin of 0.9% . The covenants on the new term loan are substantially the same as the Revolving Credit Facility. Debt Covenants On August 6, 2015, in connection with the Bridge Term Loan Agreement as discussed in Note 2 , our Revolving Credit Facility and Term Loan Credit Agreements were amended to permit the assumption of certain indebtedness of SourceGas and to increase the Recourse Leverage Ratio in certain circumstances. In these amendments, the maximum Recourse Ratio is no greater than 0.65 to 1 at the end of any fiscal quarter, but may increase to (i) 0.70 to 1 at the end of any fiscal quarter during such four fiscal quarter period where the aggregate outstanding debt assumed or incurred in connection with our acquisition of SourceGas is equal to or greater than $1.25 billion and less than $ 1.46 billion or (ii) 0.75 to 1 at the end of any fiscal quarter during such four fiscal quarter period that the aggregate outstanding debt assumed or incurred in connection with our acquisition of SourceGas is equal to or greater than $1.46 billion . Except as provided above, our Revolving Credit Facility and our Term Loan require compliance with the following financial covenant at the end of each quarter: As of September 30, 2015 Covenant Requirement Recourse Leverage Ratio 58% Less than 65% As of September 30, 2015 , we were in compliance with this covenant.

Risk Management Activities_

Risk Management Activities:	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk Management Activities	RISK MANAGEMENT ACTIVITIES Our activities in the regulated and non-regulated energy sectors expose us to a number of risks in the normal operation of our businesses. Depending on the activity, we are exposed to varying degrees of market risk and credit risk. To manage and mitigate these identified risks, we have adopted the Black Hills Corporation Risk Policies and Procedures as discussed in our 2014 Annual Report on Form 10-K/A. Market Risk Market risk is the potential loss that might occur as a result of an adverse change in market price or rate. We are exposed to the following market risks including, but not limited to: • Commodity price risk associated with our natural long position in crude oil and natural gas reserves and production; and our fuel procurement for certain of our gas-fired generation assets; and • Interest rate risk associated with our variable-rate debt. Credit Risk Credit risk is the risk of financial loss resulting from non-performance of contractual obligations by a counterparty. For production and generation activities, we attempt to mitigate our credit exposure by conducting business primarily with high credit quality entities, setting tenor and credit limits commensurate with counterparty financial strength, obtaining master netting agreements, and mitigating credit exposure with less creditworthy counterparties through parental guarantees, prepayments, letters of credit, and other security agreements. We perform ongoing credit evaluations of our customers and adjust credit limits based upon payment history and the customer’s current creditworthiness, as determined by review of their current credit information. We maintain a provision for estimated credit losses based upon historical experience and any specific customer collection issue that is identified. 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, NGLs 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 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, net of balance sheet offsetting as permitted by GAAP. The effective portion of the gain or loss on these derivatives for which we have elected cash flow hedge accounting is reported in AOCI in the accompanying Condensed Consolidated Balance Sheets and the ineffective portion, if any, is reported in Revenue in the accompanying Condensed Consolidated Statements of Income (Loss). The contract or notional amounts, terms of our commodity derivatives, and the derivative balances for our Oil and Gas segment reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 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) 258,000 5,392,500 334,500 6,582,500 391,500 7,930,000 Maximum terms in months (b) 1 1 1 1 1 1 Derivative assets, current $ — $ — $ — $ — $ — $ — Derivative assets, non-current $ — $ — $ — $ — $ — $ — Derivative liabilities, current $ — $ — $ — $ — $ — $ — Derivative liabilities, non-current $ — $ — $ — $ — $ — $ — __________ (a) Crude oil in Bbls, natural gas in MMBtus. (b) Refers to the tenor of the derivative instrument. Assets and liabilities are classified as current/non-current based on the production month hedged and the corresponding settlement of the derivative instrument. Based on September 30, 2015 prices, an $8.8 million gain would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market prices fluctuate. Utilities The operations of our utilities, including natural gas sold by our Gas Utilities and natural gas used for Electric Utility generation plants or those plants under PPAs where our Electric Utilities must provide the generation fuel (tolling agreements), expose our utility customers to volatility in natural gas prices. Therefore, as allowed or required by state utility commissions, we have entered into commission approved hedging programs utilizing natural gas futures, options and basis swaps to reduce our customers’ underlying exposure to these fluctuations. These transactions are considered derivatives, and in accordance with accounting standards for derivatives and hedging, mark-to-market adjustments are recorded as Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets, net of balance sheet offsetting as permitted by GAAP. Unrealized and realized gains and losses, as well as option premiums and commissions on these transactions are recorded as Regulatory assets or Regulatory liabilities in the accompanying Condensed Consolidated Balance Sheets in accordance with state commission guidelines. When the related costs are recovered through our rates, the hedging activity is recognized in the Condensed Consolidated Statements of Income (Loss), or the Condensed Consolidated Statements of Comprehensive Income (Loss). The contract or notional amounts and terms of the natural gas derivative commodity instruments held at our Utilities were as follows, as of: September 30, 2015 December 31, 2014 September 30, 2014 Notional (MMBtus) Maximum Term (months) (a) Notional (MMBtus) Maximum Term (months) (a) Notional (MMBtus) Maximum Term (months) (a) Natural gas futures purchased 17,180,000 63 19,370,000 72 16,290,000 74 Natural gas options purchased 6,300,000 6 4,020,000 8 7,070,000 6 Natural gas basis swaps purchased 12,980,000 51 12,005,000 60 12,025,000 63 __________ (a) Term reflects the maximum forward period hedged. We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheets as of (in thousands): September 30, 2015 December 31, 2014 September 30, 2014 Derivative assets, current $ — $ — $ — Derivative assets, non-current $ — $ — $ — Derivative liabilities, non-current $ — $ — $ — Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities $ 23,678 $ 18,740 $ 7,470 Financing Activities We entered into floating-to-fixed interest rate swap agreements to reduce our exposure to interest rate fluctuations associated with our floating rate debt obligations. The contract or notional amounts, terms of our interest rate swaps and the interest rate swaps balances reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 Interest Rate Swaps (a) Interest Rate Swaps (a) Interest Rate Swaps (a) Notional $ 75,000 $ 75,000 $ 75,000 Weighted average fixed interest rate 4.97 % 4.97 % 4.97 % Maximum terms in years 1.33 2.00 2.25 Derivative liabilities, current $ 3,312 $ 3,340 $ 3,397 Derivative liabilities, non-current $ 722 $ 2,680 $ 3,273 __________ (a) These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related borrowings. Based on September 30, 2015 market interest rates and balances related to our interest rate swaps, a loss of approximately $3.3 million would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. Estimated and actual realized gains or losses will change during future periods as market interest rates change. Cash Flow Hedges The impacts of cash flow hedges on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands): Three Months Ended September 30, 2015 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (898 ) Interest expense $ (1,603 ) $ — Commodity derivatives 5,280 Revenue 3,109 — Total $ 4,382 $ 1,506 $ — Three Months Ended September 30, 2014 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ 152 Interest expense $ (925 ) $ — Commodity derivatives 4,833 Revenue (1,135 ) — Total $ 4,985 $ (2,060 ) $ — Nine Months Ended September 30, 2015 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (2,674 ) Interest expense $ (4,709 ) $ — Commodity derivatives 6,800 Revenue 10,707 — Total $ 4,126 $ 5,998 $ — Nine Months Ended September 30, 2014 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (277 ) Interest expense $ (2,745 ) $ — Commodity derivatives (1,376 ) Revenue (2,697 ) — Total $ (1,653 ) $ (5,442 ) $ —

Fair Value Measurements_

Fair Value Measurements:	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Derivative Financial Instruments The accounting guidance for fair value measurements requires certain disclosures about assets and liabilities measured at fair value. This guidance establishes a hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the placement within the fair value hierarchy levels. We record transfers, if necessary, between levels at the end of the reporting period for all of our financial instruments. For additional information see Notes 1, 8, 9 and 10 to the Consolidated Financial Statements included in our 2014 Annual Report on Form 10-K/A 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 contracts for our Oil and Gas segment are valued using the market approach and include exchange-traded futures and basis swaps. Fair value was derived using exchange quoted settlement 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. Utilities Segments: • The commodity contracts for our Utilities Segments, valued using the market approach, include exchange-traded futures, options and basis swaps (Level 2) for natural gas contracts. For Level 2 assets and liabilities, fair value was derived using broker quotes validated by the exchange settlement pricing for the applicable contract. Corporate Activities: • The interest rate swaps are valued using the market approach. We establish fair value by obtaining price quotes directly from the counterparty which are based on the floating three-month LIBOR curve for the term of the contract. The fair value obtained from the counterparty is then validated by utilizing a nationally recognized service that obtains observable inputs to compute fair value for the same instrument. In addition, the fair value for the interest rate swap derivatives includes a CVA component. The CVA considers the fair value of the interest rate swap and the probability of default based on the life of the contract. For the probability of a default component, we utilize observable inputs supporting a Level 2 disclosure by using our credit default spread, if available, or a generic credit default spread curve that takes into account our credit ratings. Recurring Fair Value Measurements There have been no significant transfers between Level 1 and Level 2 derivative balances. Amounts included in cash collateral and counterparty netting in the following tables represent the impact of legally enforceable master netting agreements that allow us to settle positive and negative positions, netting of asset and liability positions permitted in accordance with accounting standards for offsetting as well as cash collateral posted with the same counterparties. The following tables set forth by level within the fair value hierarchy our gross assets and gross liabilities and related offsetting cash collateral and counterparty netting as permitted by GAAP that were accounted for at fair value on a recurring basis for derivative instruments. As of September 30, 2015 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 6,642 — (6,642 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 4,622 — (4,622 ) — Commodity derivatives — Utilities — 3,123 — (3,123 ) — Total $ — $ 14,387 $ — $ (14,387 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — — — — — Options -- Gas — — — — — Basis Swaps -- Gas — 467 — (467 ) — Commodity derivatives — Utilities — 24,445 — (24,445 ) — Interest rate swaps — 4,034 — — 4,034 Total $ — $ 28,946 $ — $ (24,912 ) $ 4,034 As of December 31, 2014 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 8,599 — (8,599 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 6,558 — (6,558 ) — Commodity derivatives —Utilities — 2,389 — (2,389 ) — Total $ — $ 17,546 $ — $ (17,546 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — — — — — Options -- Gas — — — — — Basis Swaps -- Gas — 473 — (473 ) — Commodity derivatives — Utilities — 19,303 — (19,303 ) — Interest rate swaps — 6,020 — — 6,020 Total $ — $ 25,796 $ — $ (19,776 ) $ 6,020 As of September 30, 2014 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 322 — (322 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 1,545 — (1,545 ) — Commodity derivatives — Utilities — 4,029 — (4,029 ) — Total $ — $ 5,896 $ — $ (5,896 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 487 — (487 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 865 — (865 ) — Commodity derivatives — Utilities — 8,679 — (8,679 ) — Interest rate swaps — 6,670 — — 6,670 Total $ — $ 16,701 $ — $ (10,031 ) $ 6,670 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 aside from 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 September 30, 2015 , December 31, 2014 , and September 30, 2014 , 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 September 30, 2015 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 9,181 $ — Commodity derivatives Derivative assets — non-current 2,083 — Commodity derivatives Derivative liabilities — current — 375 Commodity derivatives Derivative liabilities — non-current — 92 Interest rate swaps Derivative liabilities — current — 3,312 Interest rate swaps Derivative liabilities — non-current — 722 Total derivatives designated as hedges $ 11,264 $ 4,501 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 8,427 Commodity derivatives Derivative liabilities — non-current — 12,895 Total derivatives not designated as hedges $ — $ 21,322 As of December 31, 2014 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 10,391 $ — Commodity derivatives Derivative assets — non-current 4,766 — Commodity derivatives Derivative liabilities — current — 185 Commodity derivatives Derivative liabilities — non-current — 288 Interest rate swaps Derivative liabilities — current — 3,340 Interest rate swaps Derivative liabilities — non-current — 2,680 Total derivatives designated as hedges $ 15,157 $ 6,493 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 8,032 Commodity derivatives Derivative liabilities — non-current — 8,882 Total derivatives not designated as hedges $ — $ 16,914 As of September 30, 2014 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 1,174 $ — Commodity derivatives Derivative assets — non-current 692 — Commodity derivatives Derivative liabilities — current — 497 Commodity derivatives Derivative liabilities — non-current — 856 Interest rate swaps Derivative liabilities — current — 3,397 Interest rate swaps Derivative liabilities — non-current — 3,273 Total derivatives designated as hedges $ 1,866 $ 8,023 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 48 Commodity derivatives Derivative liabilities — non-current — 4,602 Total derivatives not designated as hedges $ — $ 4,650

Fair Value of Financial Instrum

Fair Value of Financial Instruments:	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	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: September 30, 2015 December 31, 2014 September 30, 2014 Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Cash and cash equivalents (a) $ 38,841 $ 38,841 $ 21,218 $ 21,218 $ 11,939 $ 11,939 Restricted cash and equivalents (a) $ 2,462 $ 2,462 $ 2,056 $ 2,056 $ 1,918 $ 1,918 Notes payable (a) $ 117,900 $ 117,900 $ 75,000 $ 75,000 $ 184,000 $ 184,000 Long-term debt, including current maturities (b) $ 1,567,797 $ 1,718,964 $ 1,542,589 $ 1,734,555 $ 1,382,519 $ 1,547,359 __________ (a) Carrying value approximates fair value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates, and therefore is classified in Level 1 in the fair value hierarchy. (b) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss):	9 Months Ended
	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss)	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 September 30, 2015 September 30, 2014 September 30, 2015 September 30, 2014 Gains (losses) on cash flow hedges: Interest rate swaps Interest expense $ 1,603 $ 925 $ 4,709 $ 2,745 Commodity contracts Revenue (3,109 ) 1,135 (10,707 ) 2,697 (1,506 ) 2,060 (5,998 ) 5,442 Income tax Income tax benefit (expense) 558 (732 ) 2,548 (1,931 ) Reclassification adjustments related to cash flow hedges, net of tax $ (948 ) $ 1,328 $ (3,450 ) $ 3,511 Amortization of defined benefit plans: Prior service cost Utilities - Operations and maintenance $ (26 ) $ (26 ) $ (80 ) $ (77 ) Non-regulated energy operations and maintenance (29 ) (22 ) (86 ) (93 ) Actuarial gain (loss) Utilities - Operations and maintenance 454 158 1,362 473 Non-regulated energy operations and maintenance 252 88 754 274 651 198 1,950 577 Income tax Income tax benefit (expense) (228 ) (69 ) (684 ) (202 ) Reclassification adjustments related to defined benefit plans, net of tax $ 423 $ 129 $ 1,266 $ 375 Balances by classification included within Accumulated other comprehensive income (loss) on the accompanying Condensed Consolidated Balance Sheets are as follows (in thousands): Derivatives Designated as Cash Flow Hedges Employee Benefit Plans Total Balance as of December 31, 2013 $ (7,133 ) $ (10,289 ) $ (17,422 ) Other comprehensive income (loss), net of tax (1,478 ) 311 (1,167 ) Balance as of March 31, 2014 (8,611 ) (9,978 ) (18,589 ) Other comprehensive income (loss), net of tax (556 ) (296 ) (852 ) Balance as of June 30, 2014 (9,167 ) (10,274 ) (19,441 ) Other comprehensive income (loss), net of tax 4,473 129 4,602 Ending Balance September 30, 2014 $ (4,694 ) $ (10,145 ) $ (14,839 ) Balance as of December 31, 2014 $ 5,093 $ (20,137 ) $ (15,044 ) Other comprehensive income (loss), net of tax 595 395 990 Balance as of March 31, 2015 5,688 (19,742 ) (14,054 ) Other comprehensive income (loss), net of tax 422 (3,227 ) (2,805 ) Balance as of June 30, 2015 6,110 (22,969 ) (16,859 ) Other comprehensive income (loss), net of tax 1,825 423 2,248 Ending Balance September 30, 2015 $ 7,935 $ (22,546 ) $ (14,611 )

Supplemental Disclosure of Cash

Supplemental Disclosure of Cash Flow Information:	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure of Cash Flow Information	SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION Nine months ended September 30, 2015 September 30, 2014 (in thousands) Non-cash investing and financing activities from continuing operations— Property, plant and equipment acquired with accrued liabilities $ 52,314 $ 52,484 Increase (decrease) in capitalized assets associated with asset retirement obligations $ — $ (2,785 ) Cash (paid) refunded during the period for continuing operations— Interest (net of amounts capitalized) $ (49,797 ) $ (46,086 ) Income taxes, net $ (1,202 ) $ (396 )

Employee Benefit Plans_

Employee Benefit Plans:	9 Months Ended
	Sep. 30, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Employee Benefit Plans	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 September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ 1,494 $ 1,362 $ 4,482 $ 4,086 Interest cost 3,880 3,963 11,640 11,889 Expected return on plan assets (4,867 ) (4,516 ) (14,601 ) (13,549 ) Prior service cost 15 16 45 47 Net loss (gain) 2,759 1,201 8,277 3,604 Net periodic benefit cost $ 3,281 $ 2,026 $ 9,843 $ 6,077 Defined Benefit Postretirement Healthcare Plans The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plans were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ 464 $ 425 $ 1,392 $ 1,275 Interest cost 450 480 1,350 1,439 Expected return on plan assets (33 ) (21 ) (99 ) (64 ) Prior service cost (benefit) (107 ) (107 ) (321 ) (321 ) Net loss (gain) 102 40 306 120 Net periodic benefit cost $ 876 $ 817 $ 2,628 $ 2,449 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 September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ (84 ) $ 374 $ 799 $ 1,123 Interest cost 364 362 1,092 1,085 Prior service cost 1 1 3 2 Net loss (gain) 270 124 810 373 Net periodic benefit cost $ 551 $ 861 $ 2,704 $ 2,583 Contributions We anticipate that we will make contributions to the benefit plans in 2015 and 2016 . 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 Contributions Contributions Three Months Ended September 30, 2015 Nine Months Ended September 30, 2015 Anticipated for 2015 Anticipated for 2016 Defined Benefit Pension Plans $ 10,200 $ 10,200 $ — $ 10,200 Non-pension Defined Benefit Postretirement Healthcare Plans $ 939 $ 2,817 $ 939 $ 4,026 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 372 $ 1,116 $ 372 $ 1,544

Commitments and Contingencies_

Commitments and Contingencies:	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES There have been no significant changes to commitments and contingencies from those previously disclosed in Note 18 of our Notes to the Consolidated Financial Statements in our 2014 Annual Report on Form 10-K/A except for those described below and in Note 2 and in Note 19. Oil Creek Fire On June 29, 2012 , a forest and grassland fire occurred in the western Black Hills of Wyoming. A fire investigator retained by the Weston County Fire Protection District concluded that the fire was caused by the failure of a transmission structure owned, operated and maintained by Black Hills Power. On April 16, 2013, a large group of private landowners filed suit in the United States District Court for the District of Wyoming. There are approximately 36 Plaintiff groups (including property jointly owned by multiple family members or entities), or approximately 73 individually named private plaintiffs. In addition, the State of Wyoming intervened in the lawsuit. These parties asserted claims seeking recovery for fire suppression, reclamation and rehabilitation costs, damage to fencing and other personal property, alleged injury to timber, grass or hay, livestock and related operations, and diminished value of real estate. On September 30, 2015, we agreed to a settlement with the State of Wyoming. The settlement amount is not material to the Company. We have recorded a corresponding receivable as we believe our settlement costs are reimbursable and probable of recovery under our insurance coverage. A trial for the private landowners’ suit has been scheduled to commence in February 2016. The private landowners’ claims for damages against Black Hills Power include allegations of negligence, negligence per se, common law nuisance and trespass. In addition to claims for compensatory damages, the lawsuit sought recovery of punitive damages; however, in October 2015, the court dismissed the claim for punitive damages. At that time, the court also ruled on a motion regarding the measure of damages to be applied to this matter. Based on that standard, we estimate the current total private claims to be approximately $55 million ; however, the actual amount of allowed claims and any loss will depend on the resolution of certain factual and legal issues. We have denied and continue to vigorously defend these claims. However, civil litigation of this kind is likely to lead to settlement negotiations, including negotiations prompted by pre-trial civil court procedures. We believe such negotiations would effect a settlement of all claims. Regardless of whether the litigation is determined at trial or through settlement, we expect to incur significant investigation, legal and expert services expenses associated with the litigation. We maintain insurance coverage to limit our exposure to losses due to civil liability claims, and related litigation expense, and we will pursue recoveries to the maximum extent available under the policies. The deductible applicable to some types of claims arising out of this fire is $1.0 million . Based upon information currently available, we believe that a loss associated with settlement of pending claims is probable. Accordingly, we recorded a loss contingency liability related to these claims and we recorded a receivable for costs we believe are reimbursable and probable of recovery under our insurance coverage. Both of these entries reflect our reasonable estimate of probable future litigation expense and settlement costs; we did not base these contingencies on any determination that it is probable we would be found liable for these claims were they to be litigated. Given the uncertainty of litigation, however, a loss related to the fire, the litigation and related claims in excess of the loss we have determined to be probable is reasonably possible. We cannot reasonably estimate the amount of such possible loss because our review of damage claim documentation and related expert opinions is ongoing, and there are significant factual and legal issues to be resolved relating to potential damage claims. Further claims may be presented by other parties. We are not yet able to reasonably estimate the amount of any reasonable possible losses in excess of the amount we have accrued. Based upon information currently available, however, management does not expect the outcome of the claims to have a material adverse effect upon our consolidated financial condition, results of operations or cash flows. Dividend Restrictions Our Revolving Credit Facility and other debt obligations contain restrictions on the payment of cash dividends upon a default or event of default. As of September 30, 2015 , we were in compliance with the debt 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 September 30, 2015 : • 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 September 30, 2015 , the restricted net assets at our Utilities Group were approximately $334 million .

Impairment of Assets_

Impairment of Assets:	9 Months Ended
	Sep. 30, 2015
Asset Impairment Charges [Abstract]
Asset Impairment Charges [Text Block]	IMPAIRMENT OF ASSETS Long-lived assets Our Oil and Gas segment accounts for oil and gas activities under the full cost method of accounting. Under the full cost method, all productive and non-productive costs related to acquisition, exploration, development, abandonment and reclamation activities are capitalized. These capitalized costs, less accumulated amortization and related deferred income taxes, are subject to a ceiling test which 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 throughout 2015, we have recorded the following non-cash impairments of our oil and gas assets included in our Oil and Gas segment. In determining the ceiling value of our assets under the full cost accounting rules of the SEC, we utilized the average of the quoted prices from the first day of each month from the previous 12 months. • During the first quarter of 2015, we recorded a $22 million pre-tax non-cash impairment of oil and gas assets included in our Oil and Gas segment. For natural gas, the average NYMEX price was $3.88 per Mcf, adjusted to $2.69 per Mcf at the wellhead; for crude oil, the average NYMEX price was $82.72 per barrel, adjusted to $74.13 per barrel at the wellhead. • During the second quarter of 2015, we recorded a $94 million pre-tax non-cash impairment of oil and gas assets. For natural gas, the average NYMEX price was $3.39 per Mcf, adjusted to $2.14 per Mcf at the wellhead; for crude oil, the average NYMEX price was $71.68 per barrel, adjusted to $63.76 per barrel at the wellhead. • During the third quarter of 2015, we recorded a $62 million pre-tax non-cash impairment of oil and gas assets. For natural gas, the average NYMEX price was $3.06 per Mcf, adjusted to $1.72 per Mcf at the wellhead; for crude oil, the average NYMEX price was $59.21 per barrel, adjusted to $52.82 per barrel at the wellhead. Equity investments in unconsolidated subsidiaries Our Oil and Gas segment owns a 25% interest in a pipeline and gathering system, accounted for under the equity method of accounting. Due to sustained low commodity prices, recurring operating losses and future expectations we reviewed this investment interest for impairment utilizing the other-than-temporary impairment model under ASC 820, Fair Value Measurements. We valued this investment applying a market method approach utilizing assumptions consistent with similar known and measurable transactions. The carrying amount of this equity method investment exceeded the fair value, and we concluded the decline is considered to be other than temporary. As a result we recorded a pre-tax impairment loss at June 30, 2015 of $5.2 million , the difference between the carrying amount and the fair value of the investment.

Income Taxes_

Income Taxes:	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The effective tax rate differs from the federal statutory rate as follows: Three Months Ended September 30, Tax (benefit) expense 2015 2014 Federal statutory rate (35.0 )% 35.0 % State income tax (net of federal tax effect) (4.7 ) (0.2 ) Percentage depletion in excess of cost (2.0 ) (1.3 ) Accounting for uncertain tax positions adjustment 1.2 (2.9 ) Flow-through adjustments (2.4 ) (1.7 ) Inter-period tax allocation (11.2 ) 1.6 Other tax differences (0.7 ) (0.7 ) (54.8 )% 29.8 % Nine Months Ended September 30, Tax (benefit) expense 2015 2014 Federal statutory rate (35.0 )% 35.0 % State income tax (net of federal tax effect) (6.7 ) 0.7 Percentage depletion in excess of cost (4.5 ) (1.0 ) Accounting for uncertain tax positions adjustment 4.7 (0.4 ) Flow-through adjustments (4.7 ) (1.1 ) Other tax differences 1.3 0.1 (44.9 )% 33.3 % The change in our effective tax rates is primarily due to the state income tax benefit resulting from the non-cash impairments of the oil and gas properties, and the favorable impact of percentage depletion particularly at our coal mine.

Subsequent Event_

Subsequent Event:	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events [Text Block]	SUBSEQUENT EVENT Build Transfer Agreement On November 2, 2015, Black Hills Colorado Electric executed a build-transfer agreement with Invenergy Wind Development Colorado, LLC to purchase the 60 MW, $109 million Peak View Wind Project. Peak View will be built by Invenergy Wind Development Colorado, LLC approximately 30 miles south of Pueblo, Colorado, in Huerfano and Las Animas counties. The estimated cost of $109 million includes taxes, transmission infrastructure and interconnection costs. Construction is expected to start in the spring of 2016, and be completed in late 2016. Under the build transfer agreement, Black Hills Colorado Electric will make progress payments starting in late 2015, continuing through completion of the project. Ownership of Peak View will transfer prior to commercial operation to Black Hills Colorado Electric and will be operated as a utility-owned asset. BHC has guaranteed the full and complete payment and performance on behalf of Black Hills Colorado Electric. Interest Rate Swap Lock On October 2, 2015, we executed a 10 year, $250 million notional, 2.29% swap lock to hedge the risks of interest rate movement between the hedge date and the expected pricing date for our anticipated long-term debt financing. The swap will be accounted for as a cash flow hedge and any gain or loss will be recorded in Accumulated Other Comprehensive Income (loss). The forward-starting interest rate swap can be used to lock-in interest rates on future debt issuances we anticipate completing in 2016. The swap has a mandatory termination date of April 12, 2027.

Management's Statement_ Correct

Management's Statement: Correction of Immaterial Errors (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]	The impact of the errors relate entirely to our Oil and Gas segment. CONDENSED CONSOLIDATED STATEMENTS OF INCOME For the Three Months Ended September 30, 2014 For the Nine Months Ended September 30, 2014 As Reported Adjustments As Revised As Reported Adjustments As Revised (in thousands, expect per share amounts) Depreciation, depletion and amortization $ 37,463 $ (835 ) $ 36,628 $ 110,258 $ (2,504 ) $ 107,754 Total operating expenses $ 217,683 $ (835 ) $ 216,848 $ 824,914 $ (2,504 ) $ 822,410 Operating income (loss) $ 54,404 $ 835 $ 55,239 $ 190,579 $ 2,504 $ 193,083 Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes $ 38,168 $ 835 $ 39,003 $ 142,124 $ 2,504 $ 144,628 Income tax benefit (expense) $ (11,332 ) $ (308 ) $ (11,640 ) $ (47,349 ) $ (923 ) $ (48,272 ) Net income (loss) available for common stock $ 26,836 $ 527 $ 27,363 $ 94,774 $ 1,581 $ 96,355 Earnings (loss) per share of common stock: Earnings (loss) per share, Basic $ 0.60 $ 0.02 $ 0.62 $ 2.14 $ 0.03 $ 2.17 Earnings (loss) per share, Diluted $ 0.60 $ 0.01 $ 0.61 $ 2.13 $ 0.03 $ 2.16 CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) For the Three Months Ended September 30, 2014 For the Nine Months Ended September 30, 2014 (in thousands) As Reported Adjustments As Revised As Reported Adjustments As Revised Net income (loss) available for common stock $ 26,836 $ 527 $ 27,363 $ 94,774 $ 1,581 $ 96,355 Comprehensive income (loss) $ 31,438 $ 527 $ 31,965 $ 97,357 $ 1,581 $ 98,938 CONDENSED CONSOLIDATED BALANCE SHEETS As of September 30, 2014 As Reported Adjustments As Revised (in thousands) Accumulated depreciation and depletion $ (1,338,509 ) $ (34,738 ) $ (1,373,247 ) Total property, plant and equipment, net $ 3,155,187 $ (34,738 ) $ 3,120,449 TOTAL ASSETS $ 4,073,262 $ (34,738 ) $ 4,038,524 Deferred income tax liability, non-current $ 506,166 $ (12,071 ) $ 494,095 Total deferred credits and other liabilities $ 881,308 $ (12,071 ) $ 869,237 Retained earnings $ 582,800 $ (22,667 ) $ 560,133 Total stockholders' equity $ 1,357,392 $ (22,667 ) $ 1,334,725 TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY $ 4,073,262 $ (34,738 ) $ 4,038,524 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Nine Months Ended September 30, 2014 As Reported Adjustments As Revised (in thousands) Net income (loss) available for common stock $ 94,774 $ 1,581 $ 96,355 Adjustments to reconcile net income (loss) to net cash provided by operating activities: Depreciation, depletion and amortization $ 110,258 $ (2,504 ) $ 107,754 Deferred income taxes $ 48,007 $ 923 $ 48,930 Net cash provided by (used in) operating activities $ 239,157 $ — $ 239,157 The Notes to the Condensed Consolidated Financial Statements have been revised to reflect the correction of these errors for all periods presented.

Business Segment Information_ B

Business Segment Information: Business Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting Information, Additional Information [Abstract]
Schedule of Segment Reporting Information	Segment information and Corporate activities included in the accompanying Condensed Consolidated Statements of Income (Loss) were as follows (in thousands): Three Months Ended September 30, 2015 External Operating Revenue Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 182,263 $ 2,547 $ 21,982 Gas 68,934 — 1,630 Non-regulated Energy: Power Generation 2,123 21,128 9,067 Coal Mining 8,890 8,076 3,047 Oil and Gas (a) 9,895 — (39,769 ) Corporate activities (c) — — (5,900 ) Inter-company eliminations — (31,751 ) — Total $ 272,105 $ — $ (9,943 ) Three Months Ended September 30, 2014 External Operating Revenue Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 171,395 $ 3,156 $ 18,154 Gas 78,735 — 1,597 Non-regulated Energy: Power Generation 1,602 20,419 7,829 Coal Mining 6,884 8,689 2,638 Oil and Gas 13,471 — (2,583 ) Corporate activities — — (272 ) Inter-company eliminations — (32,264 ) — Total $ 272,087 $ — $ 27,363 Nine Months Ended September 30, 2015 External Operating Revenues Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 534,988 $ 8,480 $ 58,613 Gas 386,011 — 27,007 Non-regulated Energy: Power Generation 5,782 62,452 24,761 Coal Mining 26,084 23,541 9,106 Oil and Gas (a)(b) 33,481 — (130,079 ) Corporate activities (c) — — (7,343 ) Inter-company eliminations — (94,473 ) — Total $ 986,346 $ — $ (17,935 ) Nine Months Ended September 30, 2014 External Operating Revenues Inter-company Operating Revenue Net Income (Loss) Utilities: Electric $ 508,230 $ 10,307 $ 44,156 Gas 440,571 — 28,289 Non-regulated Energy: Power Generation 4,138 62,211 23,096 Coal Mining 19,085 26,637 7,118 Oil and Gas 43,469 — (5,211 ) Corporate activities — — (1,093 ) Inter-company eliminations — (99,155 ) — Total $ 1,015,493 $ — $ 96,355 __________ (a) Net income (loss) for the three and nine months ended September 30, 2015 included non-cash after-tax ceiling test impairments of $36 million and $113 million , respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (b) Net income (loss) for the nine months ended September 30, 2015 included a non-cash after-tax impairment to equity investments of $3.4 million . See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (c) Net income (loss) for the three and nine months ended September 30, 2015 included incremental, non-recurring acquisition costs, net of tax of $2.8 million and $3.0 million , respectively and after-tax internal labor costs attributable to the acquisition of $1.2 million and $1.8 million , respectively. See Note 2 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.
Reconciliation of Assets from Segment to Consolidated	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: September 30, 2015 December 31, 2014 September 30, 2014 Utilities: Electric (a) $ 2,846,931 $ 2,748,680 $ 2,671,601 Gas 831,802 906,922 827,069 Non-regulated Energy: Power Generation (a) 78,666 76,945 64,359 Coal Mining 78,000 74,407 74,130 Oil and Gas (b) (c) 280,842 332,343 296,043 Corporate activities 130,321 106,605 105,322 Total assets $ 4,246,562 $ 4,245,902 $ 4,038,524 __________ (a) The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under accounting for a capital lease. (b) As a result of continued low commodity prices during 2015, we recorded non-cash impairments of oil and gas assets included in our Oil and Gas segment of $62 million and $178 million for the for the three and nine months ended September 30, 2015 , respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q. (c) Includes a non-cash impairment of our Oil and Gas equity investments of $5.2 million for the nine months ended September 30, 2015 . See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.

Accounts Receivable_ Accounts R

Accounts Receivable: Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2015
Receivables [Abstract]
Accounts Receivable and Allowance for Doubtful Accounts	Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: Accounts Unbilled Less Allowance for Accounts September 30, 2015 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 43,337 $ 35,069 $ (720 ) $ 77,686 Gas Utilities 18,349 10,140 (618 ) 27,871 Power Generation 1,186 — — 1,186 Coal Mining 2,684 — — 2,684 Oil and Gas 4,522 — (13 ) 4,509 Corporate 1,566 — — 1,566 Total $ 71,644 $ 45,209 $ (1,351 ) $ 115,502 Accounts Unbilled Less Allowance for Accounts December 31, 2014 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 59,714 $ 26,474 $ (722 ) $ 85,466 Gas Utilities 47,394 45,546 (781 ) 92,159 Power Generation 1,369 — — 1,369 Coal Mining 3,151 — — 3,151 Oil and Gas 5,305 — (13 ) 5,292 Corporate 2,555 — — 2,555 Total $ 119,488 $ 72,020 $ (1,516 ) $ 189,992 Accounts Unbilled Less Allowance for Accounts September 30, 2014 Receivable, Trade Revenue Doubtful Accounts Receivable, net Electric Utilities $ 53,717 $ 21,485 $ (724 ) $ 74,478 Gas Utilities 23,409 13,218 (740 ) 35,887 Power Generation 1,368 — — 1,368 Coal Mining 2,563 — — 2,563 Oil and Gas 7,657 — (13 ) 7,644 Corporate 1,459 — — 1,459 Total $ 90,173 $ 34,703 $ (1,477 ) $ 123,399

Regulatory Accounting_ Regulato

Regulatory Accounting: Regulatory Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Schedule of Regulatory Assets and Liabilities	We had the following regulatory assets and liabilities (in thousands): Maximum As of As of As of Amortization (in years) September 30, 2015 December 31, 2014 September 30, 2014 Regulatory assets Deferred energy and fuel cost adjustments - current (a) (d) 1 $ 25,354 $ 23,820 $ 26,211 Deferred gas cost adjustments (a)(d) 2 9,358 37,471 42,400 Gas price derivatives (a) 7 23,681 18,740 7,470 AFUDC (b) 45 12,580 12,358 12,411 Employee benefit plans (c) (e) 12 95,779 97,126 64,908 Environmental (a) subject to approval 1,209 1,314 1,314 Asset retirement obligations (a) 44 675 3,287 3,282 Bond issue cost (a) 23 3,169 3,276 3,311 Renewable energy standard adjustment (b) 5 5,102 9,622 12,007 Flow through accounting (c) 35 28,585 25,887 25,157 Decommissioning costs (f) 10 16,353 12,484 — Other regulatory assets (a) 15 12,454 12,454 10,395 $ 234,299 $ 257,839 $ 208,866 Regulatory liabilities Deferred energy and gas costs (a) (d) 1 $ 9,899 $ 6,496 $ 5,535 Employee benefit plans (c) (e) 12 53,140 53,139 34,409 Cost of removal (a) 44 86,946 78,249 71,362 Other regulatory liabilities (c) 25 7,826 10,947 8,378 $ 157,811 $ 148,831 $ 119,684 __________ (a) Recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively. (d) Our deferred energy, fuel cost, and gas cost adjustments represent the cost of electricity and gas delivered to our electric and gas utility customers that is either higher or lower than current rates and will be recovered or refunded in future rates. Fluctuations in deferred gas cost adjustments compared to the same period in the prior year are primarily due to higher natural gas prices driven by demand and market conditions from the peak winter heating season in the first part of 2014. Our electric and gas utilities file periodic quarterly, semi-annual, and/or annual filings to recover these costs based on the respective cost mechanisms approved by their applicable state utility commissions. (e) Increase compared to September 30, 2014 was driven by a decrease in the discount rate and a change in the mortality tables used in employee benefit plan estimates. (f) Black Hills Power has approximately $13 million of decommissioning costs associated with the retirements of the Neil Simpson I and Ben French power plants that are allowed a rate of return, in addition to recovery of costs.

Materials, Supplies and Fuel_ M

Materials, Supplies and Fuel: Materials, Supplies and Fuel (Tables)	9 Months Ended
	Sep. 30, 2015
Inventory, Net [Abstract]
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: September 30, 2015 December 31, 2014 September 30, 2014 Materials and supplies $ 53,838 $ 49,555 $ 52,682 Fuel - Electric Utilities 6,139 6,637 7,108 Natural gas in storage held for distribution 30,372 34,999 45,936 Total materials, supplies and fuel $ 90,349 $ 91,191 $ 105,726

Goodwill_ Goodwill (Tables)

Goodwill: Goodwill (Tables)	9 Months Ended
	Sep. 30, 2015
Goodwill [Abstract]
Schedule of Goodwill	Following is a summary of Goodwill included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: Electric Utilities Gas Utilities Power Generation Total Ending balance at December 31, 2014 $ 250,487 $ 94,144 $ 8,765 $ 353,396 Additions (a) 6,131 — — 6,131 Ending balance at September 30, 2015 $ 256,618 $ 94,144 $ 8,765 $ 359,527 __________ (a) Goodwill was recorded on the acquisition of Wyoming natural gas utility Energy West Wyoming, Inc., and natural gas pipeline assets from Energy West Development, Inc. completed on July 1, 2015.

Earnings Per Share_ Earnings Pe

Earnings Per Share: Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Reconciliation	A reconciliation of share amounts used to compute Earnings (loss) per share in the accompanying Condensed Consolidated Statements of Income (Loss) was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net income (loss) available for common stock $ (9,943 ) $ 27,363 $ (17,935 ) $ 96,355 Weighted average shares - basic 44,635 44,415 44,598 44,382 Dilutive effect of: Equity compensation — 193 — 202 Weighted average shares - diluted 44,635 44,608 44,598 44,584
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	In addition to these potentially dilutive shares excluded due to our net loss for the three and nine months ended September 30, 2015 , the following outstanding securities were also excluded in the computation of diluted net income (loss) per share as their inclusion would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Equity compensation 121 99 114 75 Anti-dilutive shares 121 99 114 75

Notes Payable and Long-term D34

Notes Payable and Long-term Debt: Notes Payable and Long-term Debt (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Schedule of Short-term Debt	We had the following short-term debt outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 Balance Outstanding Letters of Credit Balance Outstanding Letters of Credit Balance Outstanding Letters of Credit Revolving Credit Facility $ 117,900 $ 30,600 $ 75,000 $ 35,000 $ 184,000 $ 31,726
Schedule of Credit Facility Covenants	our Revolving Credit Facility and our Term Loan require compliance with the following financial covenant at the end of each quarter: As of September 30, 2015 Covenant Requirement Recourse Leverage Ratio 58% Less than 65%

Risk Management Activities_ Ris

Risk Management Activities: Risk Management Activities (Tables)	9 Months Ended
	Sep. 30, 2015
Derivative [Line Items]
Schedule of Derivative Instruments	The contract or notional amounts, terms of our interest rate swaps and the interest rate swaps balances reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 Interest Rate Swaps (a) Interest Rate Swaps (a) Interest Rate Swaps (a) Notional $ 75,000 $ 75,000 $ 75,000 Weighted average fixed interest rate 4.97 % 4.97 % 4.97 % Maximum terms in years 1.33 2.00 2.25 Derivative liabilities, current $ 3,312 $ 3,340 $ 3,397 Derivative liabilities, non-current $ 722 $ 2,680 $ 3,273 __________ (a) These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related borrowings.
Derivative Instruments, Gain (Loss)	The impacts of cash flow hedges on our Condensed Consolidated Statements of Income (Loss) were as follows (in thousands): Three Months Ended September 30, 2015 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (898 ) Interest expense $ (1,603 ) $ — Commodity derivatives 5,280 Revenue 3,109 — Total $ 4,382 $ 1,506 $ — Three Months Ended September 30, 2014 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ 152 Interest expense $ (925 ) $ — Commodity derivatives 4,833 Revenue (1,135 ) — Total $ 4,985 $ (2,060 ) $ — Nine Months Ended September 30, 2015 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (2,674 ) Interest expense $ (4,709 ) $ — Commodity derivatives 6,800 Revenue 10,707 — Total $ 4,126 $ 5,998 $ — Nine Months Ended September 30, 2014 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion) Location of Gain/(Loss) Reclassified from AOCI into Income (Effective Portion) Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion) Location of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion) Interest rate swaps $ (277 ) Interest expense $ (2,745 ) $ — Commodity derivatives (1,376 ) Revenue (2,697 ) — Total $ (1,653 ) $ (5,442 ) $ —
Oil and Gas [Member]
Derivative [Line Items]
Schedule of Derivative Instruments	The contract or notional amounts, terms of our commodity derivatives, and the derivative balances for our Oil and Gas segment reflected on the Condensed Consolidated Balance Sheets were as follows (dollars in thousands) as of: September 30, 2015 December 31, 2014 September 30, 2014 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) 258,000 5,392,500 334,500 6,582,500 391,500 7,930,000 Maximum terms in months (b) 1 1 1 1 1 1 Derivative assets, current $ — $ — $ — $ — $ — $ — Derivative assets, non-current $ — $ — $ — $ — $ — $ — Derivative liabilities, current $ — $ — $ — $ — $ — $ — Derivative liabilities, non-current $ — $ — $ — $ — $ — $ — __________ (a) Crude oil in Bbls, natural gas in MMBtus. (b) Refers to the tenor of the derivative instrument. Assets and liabilities are classified as current/non-current based on the production month hedged and the corresponding settlement of the derivative instrument.
Utilities Group [Member]
Derivative [Line Items]
Schedule of Derivative Instruments	We had the following derivative balances related to the hedges in our Utilities reflected in our Condensed Consolidated Balance Sheets as of (in thousands): September 30, 2015 December 31, 2014 September 30, 2014 Derivative assets, current $ — $ — $ — Derivative assets, non-current $ — $ — $ — Derivative liabilities, non-current $ — $ — $ — Net unrealized (gain) loss included in Regulatory assets or Regulatory liabilities $ 23,678 $ 18,740 $ 7,470
Contract or Notional Amounts and Terms of Commodity Derivatives	The contract or notional amounts and terms of the natural gas derivative commodity instruments held at our Utilities were as follows, as of: September 30, 2015 December 31, 2014 September 30, 2014 Notional (MMBtus) Maximum Term (months) (a) Notional (MMBtus) Maximum Term (months) (a) Notional (MMBtus) Maximum Term (months) (a) Natural gas futures purchased 17,180,000 63 19,370,000 72 16,290,000 74 Natural gas options purchased 6,300,000 6 4,020,000 8 7,070,000 6 Natural gas basis swaps purchased 12,980,000 51 12,005,000 60 12,025,000 63 __________ (a) Term reflects the maximum forward period hedged.

Fair Value Measurements_ Fair V

Fair Value Measurements: Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Schedule of Fair Value Hierarchy, Measured on Recurring Basis	The following tables set forth by level within the fair value hierarchy our gross assets and gross liabilities and related offsetting cash collateral and counterparty netting as permitted by GAAP that were accounted for at fair value on a recurring basis for derivative instruments. As of September 30, 2015 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 6,642 — (6,642 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 4,622 — (4,622 ) — Commodity derivatives — Utilities — 3,123 — (3,123 ) — Total $ — $ 14,387 $ — $ (14,387 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — — — — — Options -- Gas — — — — — Basis Swaps -- Gas — 467 — (467 ) — Commodity derivatives — Utilities — 24,445 — (24,445 ) — Interest rate swaps — 4,034 — — 4,034 Total $ — $ 28,946 $ — $ (24,912 ) $ 4,034 As of December 31, 2014 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 8,599 — (8,599 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 6,558 — (6,558 ) — Commodity derivatives —Utilities — 2,389 — (2,389 ) — Total $ — $ 17,546 $ — $ (17,546 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — — — — — Options -- Gas — — — — — Basis Swaps -- Gas — 473 — (473 ) — Commodity derivatives — Utilities — 19,303 — (19,303 ) — Interest rate swaps — 6,020 — — 6,020 Total $ — $ 25,796 $ — $ (19,776 ) $ 6,020 As of September 30, 2014 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 322 — (322 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 1,545 — (1,545 ) — Commodity derivatives — Utilities — 4,029 — (4,029 ) — Total $ — $ 5,896 $ — $ (5,896 ) $ — Liabilities: Commodity derivatives — Oil and Gas Options -- Oil $ — $ — $ — $ — $ — Basis Swaps -- Oil — 487 — (487 ) — Options -- Gas — — — — — Basis Swaps -- Gas — 865 — (865 ) — Commodity derivatives — Utilities — 8,679 — (8,679 ) — Interest rate swaps — 6,670 — — 6,670 Total $ — $ 16,701 $ — $ (10,031 ) $ 6,670
Schedule of Derivative Instruments Balance Sheet Location	The following tables present the fair value and balance sheet classification of our derivative instruments (in thousands): As of September 30, 2015 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 9,181 $ — Commodity derivatives Derivative assets — non-current 2,083 — Commodity derivatives Derivative liabilities — current — 375 Commodity derivatives Derivative liabilities — non-current — 92 Interest rate swaps Derivative liabilities — current — 3,312 Interest rate swaps Derivative liabilities — non-current — 722 Total derivatives designated as hedges $ 11,264 $ 4,501 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 8,427 Commodity derivatives Derivative liabilities — non-current — 12,895 Total derivatives not designated as hedges $ — $ 21,322 As of December 31, 2014 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 10,391 $ — Commodity derivatives Derivative assets — non-current 4,766 — Commodity derivatives Derivative liabilities — current — 185 Commodity derivatives Derivative liabilities — non-current — 288 Interest rate swaps Derivative liabilities — current — 3,340 Interest rate swaps Derivative liabilities — non-current — 2,680 Total derivatives designated as hedges $ 15,157 $ 6,493 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 8,032 Commodity derivatives Derivative liabilities — non-current — 8,882 Total derivatives not designated as hedges $ — $ 16,914 As of September 30, 2014 Balance Sheet Location Fair Value of Asset Derivatives Fair Value of Liability Derivatives Derivatives designated as hedges: Commodity derivatives Derivative assets — current $ 1,174 $ — Commodity derivatives Derivative assets — non-current 692 — Commodity derivatives Derivative liabilities — current — 497 Commodity derivatives Derivative liabilities — non-current — 856 Interest rate swaps Derivative liabilities — current — 3,397 Interest rate swaps Derivative liabilities — non-current — 3,273 Total derivatives designated as hedges $ 1,866 $ 8,023 Derivatives not designated as hedges: Commodity derivatives Derivative assets — current $ — $ — Commodity derivatives Derivative assets — non-current — — Commodity derivatives Derivative liabilities — current — 48 Commodity derivatives Derivative liabilities — non-current — 4,602 Total derivatives not designated as hedges $ — $ 4,650

Fair Value of Financial Instr37

Fair Value of Financial Instruments: Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
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: September 30, 2015 December 31, 2014 September 30, 2014 Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Cash and cash equivalents (a) $ 38,841 $ 38,841 $ 21,218 $ 21,218 $ 11,939 $ 11,939 Restricted cash and equivalents (a) $ 2,462 $ 2,462 $ 2,056 $ 2,056 $ 1,918 $ 1,918 Notes payable (a) $ 117,900 $ 117,900 $ 75,000 $ 75,000 $ 184,000 $ 184,000 Long-term debt, including current maturities (b) $ 1,567,797 $ 1,718,964 $ 1,542,589 $ 1,734,555 $ 1,382,519 $ 1,547,359 __________ (a) Carrying value approximates fair value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates, and therefore is classified in Level 1 in the fair value hierarchy. (b) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

Other Comprehensive Income (L38

Other Comprehensive Income (Loss): Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Reclassification Out of Accumulated 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 September 30, 2015 September 30, 2014 September 30, 2015 September 30, 2014 Gains (losses) on cash flow hedges: Interest rate swaps Interest expense $ 1,603 $ 925 $ 4,709 $ 2,745 Commodity contracts Revenue (3,109 ) 1,135 (10,707 ) 2,697 (1,506 ) 2,060 (5,998 ) 5,442 Income tax Income tax benefit (expense) 558 (732 ) 2,548 (1,931 ) Reclassification adjustments related to cash flow hedges, net of tax $ (948 ) $ 1,328 $ (3,450 ) $ 3,511 Amortization of defined benefit plans: Prior service cost Utilities - Operations and maintenance $ (26 ) $ (26 ) $ (80 ) $ (77 ) Non-regulated energy operations and maintenance (29 ) (22 ) (86 ) (93 ) Actuarial gain (loss) Utilities - Operations and maintenance 454 158 1,362 473 Non-regulated energy operations and maintenance 252 88 754 274 651 198 1,950 577 Income tax Income tax benefit (expense) (228 ) (69 ) (684 ) (202 ) Reclassification adjustments related to defined benefit plans, net of tax $ 423 $ 129 $ 1,266 $ 375
Schedule of Accumulated Other Comprehensive Income (Loss)	Balances by classification included within Accumulated other comprehensive income (loss) on the accompanying Condensed Consolidated Balance Sheets are as follows (in thousands): Derivatives Designated as Cash Flow Hedges Employee Benefit Plans Total Balance as of December 31, 2013 $ (7,133 ) $ (10,289 ) $ (17,422 ) Other comprehensive income (loss), net of tax (1,478 ) 311 (1,167 ) Balance as of March 31, 2014 (8,611 ) (9,978 ) (18,589 ) Other comprehensive income (loss), net of tax (556 ) (296 ) (852 ) Balance as of June 30, 2014 (9,167 ) (10,274 ) (19,441 ) Other comprehensive income (loss), net of tax 4,473 129 4,602 Ending Balance September 30, 2014 $ (4,694 ) $ (10,145 ) $ (14,839 ) Balance as of December 31, 2014 $ 5,093 $ (20,137 ) $ (15,044 ) Other comprehensive income (loss), net of tax 595 395 990 Balance as of March 31, 2015 5,688 (19,742 ) (14,054 ) Other comprehensive income (loss), net of tax 422 (3,227 ) (2,805 ) Balance as of June 30, 2015 6,110 (22,969 ) (16,859 ) Other comprehensive income (loss), net of tax 1,825 423 2,248 Ending Balance September 30, 2015 $ 7,935 $ (22,546 ) $ (14,611 )

Supplemental Disclosure of Ca39

Supplemental Disclosure of Cash Flow Information: Supplemental Disclosure of Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure of Cash Flow Information	Nine months ended September 30, 2015 September 30, 2014 (in thousands) Non-cash investing and financing activities from continuing operations— Property, plant and equipment acquired with accrued liabilities $ 52,314 $ 52,484 Increase (decrease) in capitalized assets associated with asset retirement obligations $ — $ (2,785 ) Cash (paid) refunded during the period for continuing operations— Interest (net of amounts capitalized) $ (49,797 ) $ (46,086 ) Income taxes, net $ (1,202 ) $ (396 )

Employee Benefit Plans_ Employe

Employee Benefit Plans: Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit cost for the Defined Benefit Pension Plans were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ 1,494 $ 1,362 $ 4,482 $ 4,086 Interest cost 3,880 3,963 11,640 11,889 Expected return on plan assets (4,867 ) (4,516 ) (14,601 ) (13,549 ) Prior service cost 15 16 45 47 Net loss (gain) 2,759 1,201 8,277 3,604 Net periodic benefit cost $ 3,281 $ 2,026 $ 9,843 $ 6,077 Defined Benefit Postretirement Healthcare Plans The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plans were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ 464 $ 425 $ 1,392 $ 1,275 Interest cost 450 480 1,350 1,439 Expected return on plan assets (33 ) (21 ) (99 ) (64 ) Prior service cost (benefit) (107 ) (107 ) (321 ) (321 ) Net loss (gain) 102 40 306 120 Net periodic benefit cost $ 876 $ 817 $ 2,628 $ 2,449 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 September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Service cost $ (84 ) $ 374 $ 799 $ 1,123 Interest cost 364 362 1,092 1,085 Prior service cost 1 1 3 2 Net loss (gain) 270 124 810 373 Net periodic benefit cost $ 551 $ 861 $ 2,704 $ 2,583
Schedule of Defined Benefit Plans Contributions	Contributions and anticipated contributions are as follows (in thousands): Contributions Made Contributions Made Additional Contributions Contributions Three Months Ended September 30, 2015 Nine Months Ended September 30, 2015 Anticipated for 2015 Anticipated for 2016 Defined Benefit Pension Plans $ 10,200 $ 10,200 $ — $ 10,200 Non-pension Defined Benefit Postretirement Healthcare Plans $ 939 $ 2,817 $ 939 $ 4,026 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 372 $ 1,116 $ 372 $ 1,544

Income Taxes_ Income Taxes (Tab

Income Taxes: Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	INCOME TAXES The effective tax rate differs from the federal statutory rate as follows: Three Months Ended September 30, Tax (benefit) expense 2015 2014 Federal statutory rate (35.0 )% 35.0 % State income tax (net of federal tax effect) (4.7 ) (0.2 ) Percentage depletion in excess of cost (2.0 ) (1.3 ) Accounting for uncertain tax positions adjustment 1.2 (2.9 ) Flow-through adjustments (2.4 ) (1.7 ) Inter-period tax allocation (11.2 ) 1.6 Other tax differences (0.7 ) (0.7 ) (54.8 )% 29.8 % Nine Months Ended September 30, Tax (benefit) expense 2015 2014 Federal statutory rate (35.0 )% 35.0 % State income tax (net of federal tax effect) (6.7 ) 0.7 Percentage depletion in excess of cost (4.5 ) (1.0 ) Accounting for uncertain tax positions adjustment 4.7 (0.4 ) Flow-through adjustments (4.7 ) (1.1 ) Other tax differences 1.3 0.1 (44.9 )% 33.3 %

Management's Statement_ Corre42

Management's Statement: Correction of Immaterial Errors (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Statement [Abstract]
Depreciation, depletion and amortization	$ 37,768	$ 36,628	$ 116,821	$ 107,754
Total operating expenses	274,149	216,848	956,748	822,410
Operating income (loss)	(2,044)	55,239	29,598	193,083
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	(21,978)	39,003	(27,061)	144,628
Income tax expense (benefit)	12,035	(11,640)	14,640	(48,272)
Net income (loss) available for common stock	$ (9,943)	$ 27,363	$ (17,935)	$ 96,355
Total income (loss) per share, Basic	$ (0.22)	$ 0.62	$ (0.40)	$ 2.17
Total income (loss) per share, Diluted	$ (0.22)	$ 0.61	$ (0.40)	$ 2.16
Comprehensive income (loss)	$ (7,695)	$ 31,965	$ (17,502)	$ 98,938
Balance Sheet [Abstract]
Accumulated depreciation and depletion	(1,617,723)	(1,373,247)	(1,617,723)	(1,373,247)	$ (1,357,929)
Total property, plant and equipment, net	3,264,697	3,120,449	3,264,697	3,120,449	3,205,471
Total Assets	4,246,562	4,038,524	4,246,562	4,038,524	4,245,902
Deferred income tax liabilities, net, non-current	494,834	494,095	494,834	494,095	511,952
Total deferred credits and other liabilities	942,796	869,237	942,796	869,237	973,148
Retained earnings	504,864	560,133	504,864	560,133	577,249
Total stockholders’ equity	1,287,212	1,334,725	1,287,212	1,334,725	1,353,884
Total Liabilities and Stockholders' Equity	$ 4,246,562	4,038,524	4,246,562	4,038,524	$ 4,245,902
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities			365,873	239,157
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income taxes			$ (20,808)	48,930
Scenario, Previously Reported [Member]
Income Statement [Abstract]
Depreciation, depletion and amortization		37,463		110,258
Total operating expenses		217,683		824,914
Operating income (loss)		54,404		190,579
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes		38,168		142,124
Income tax expense (benefit)		(11,332)		(47,349)
Net income (loss) available for common stock		$ 26,836		$ 94,774
Total income (loss) per share, Basic		$ 0.60		$ 2.14
Total income (loss) per share, Diluted		$ 0.60		$ 2.13
Comprehensive income (loss)		$ 31,438		$ 97,357
Balance Sheet [Abstract]
Accumulated depreciation and depletion		(1,338,509)		(1,338,509)
Total property, plant and equipment, net		3,155,187		3,155,187
Total Assets		4,073,262		4,073,262
Deferred income tax liabilities, net, non-current		506,166		506,166
Total deferred credits and other liabilities		881,308		881,308
Retained earnings		582,800		582,800
Total stockholders’ equity		1,357,392		1,357,392
Total Liabilities and Stockholders' Equity		4,073,262		4,073,262
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities				239,157
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income taxes				48,007
Scenario, Adjustment [Member]
Income Statement [Abstract]
Depreciation, depletion and amortization		(835)		(2,504)
Total operating expenses		(835)		(2,504)
Operating income (loss)		835		2,504
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes		835		2,504
Income tax expense (benefit)		(308)		(923)
Net income (loss) available for common stock		$ 527		$ 1,581
Total income (loss) per share, Basic		$ 0.02		$ 0.03
Total income (loss) per share, Diluted		$ 0.01		$ 0.03
Comprehensive income (loss)		$ 527		$ 1,581
Balance Sheet [Abstract]
Accumulated depreciation and depletion		(34,738)		(34,738)
Total property, plant and equipment, net		(34,738)		(34,738)
Total Assets		(34,738)		(34,738)
Deferred income tax liabilities, net, non-current		(12,071)		(12,071)
Total deferred credits and other liabilities		(12,071)		(12,071)
Retained earnings		(22,667)		(22,667)
Total stockholders’ equity		(22,667)		(22,667)
Total Liabilities and Stockholders' Equity		$ (34,738)		(34,738)
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities				0
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income taxes				$ 923

Acquisition_ Acquisition (Detai

Acquisition: Acquisition (Details) $ in Millions	Jul. 12, 2015USD ($)customerutility	Sep. 30, 2015USD ($)	Aug. 06, 2015USD ($)
Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, maximum Recourse Ratio		0.65
Source Gas [Member]
Business Acquisition [Line Items]
Number of regulated natural gas utilities, acquiree | utility	4
Number of customers served by acquiree | customer	425,000
Source Gas [Member]
Business Acquisition [Line Items]
Acquisition purchase price	$ 1,890
Included in purchase price - projected capital expenditures through closing	200
Included in purchase price - long-term debt to be assumed	700
Projected net purchase price	1,740
Included in purchase price - tax benefits	150
Bridge facility	1,170		$ 1,170
Source Gas [Member] | Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, maximum Recourse Ratio		0.65
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount		$ 1,460
Source Gas [Member] | Revolving Credit Facility [Member] | Debt Instrument, Covenant, Trigger 1 [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, maximum Recourse Ratio		0.70
Source Gas [Member] | Revolving Credit Facility [Member] | Debt Instrument, Covenant, Trigger 2 [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, maximum Recourse Ratio		0.75
Source Gas [Member] | Bridge Loan [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, maximum Recourse Ratio		0.75
Source Gas [Member] | Minimum [Member]
Business Acquisition [Line Items]
Proceeds From Issuance Of Common Stock And Convertible Debt	450
Proceeds from Convertible Debt	200
Proceeds from issuance of debt	450
Source Gas [Member] | Minimum [Member] | Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount		$ 1,250
Source Gas [Member] | Maximum [Member]
Business Acquisition [Line Items]
Proceeds From Issuance Of Common Stock And Convertible Debt	600
Proceeds from Convertible Debt	300
Proceeds from issuance of debt	$ 550
Source Gas [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount		$ 1,460

Business Segment Information_ I

Business Segment Information: Information Relating to Segment Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Segment Reporting Information
Revenue	$ 272,105		$ 272,087	$ 986,346		$ 1,015,493
Net Income (Loss)	(9,943)		27,363	(17,935)		96,355
Inter-company eliminations [Member]
Segment Reporting Information
Revenue	(31,751)		(32,264)	(94,473)		(99,155)
Net Income (Loss)	0		0	0		0
Corporate activities[Member]
Segment Reporting Information
Revenue	0		0	0		0
Net Income (Loss)	(5,900)	[1]	(272)	(7,343)	[1]	(1,093)
Consolidation, Eliminations [Member]
Segment Reporting Information
Revenue	0		0	0		0
Electric Utilities [Member]
Segment Reporting Information
Revenue	182,263		171,395	534,988		508,230
Net Income (Loss)	21,982		18,154	58,613		44,156
Electric Utilities [Member] | Inter-company eliminations [Member]
Segment Reporting Information
Revenue	2,547		3,156	8,480		10,307
Gas Utilities [Member]
Segment Reporting Information
Revenue	68,934		78,735	386,011		440,571
Net Income (Loss)	1,630		1,597	27,007		28,289
Gas Utilities [Member] | Inter-company eliminations [Member]
Segment Reporting Information
Revenue	0		0	0		0
Power Generation [Member]
Segment Reporting Information
Revenue	2,123		1,602	5,782		4,138
Net Income (Loss)	9,067		7,829	24,761		23,096
Power Generation [Member] | Inter-company eliminations [Member]
Segment Reporting Information
Revenue	21,128		20,419	62,452		62,211
Coal Mining [Member]
Segment Reporting Information
Revenue	8,890		6,884	26,084		19,085
Net Income (Loss)	3,047		2,638	9,106		7,118
Coal Mining [Member] | Inter-company eliminations [Member]
Segment Reporting Information
Revenue	8,076		8,689	23,541		26,637
Oil and Gas [Member]
Segment Reporting Information
Revenue	9,895		13,471	33,481		43,469
Net Income (Loss)	(39,769)	[2]	(2,583)	(130,079)	[2],[3]	(5,211)
Impairment of Oil and Gas Properties Net of Tax	36,000			113,000
Equity Method Investment, Other than Temporary Impairment, Net of Income Taxes				3,400
Oil and Gas [Member] | Inter-company eliminations [Member]
Segment Reporting Information
Revenue	0		$ 0	0		$ 0
Incremental, Non-Recurring Acquisition Costs (Net of Tax) [Member] | Corporate activities[Member]
Segment Reporting Information
Business Acquisition, Transaction Costs	2,800			3,000
Labor (Net Of Tax) [Member] | Corporate activities[Member]
Segment Reporting Information
Business Acquisition, Transaction Costs	$ 1,200			$ 1,800
[1]	Net income (loss) for the three and nine months ended September 30, 2015 included incremental, non-recurring acquisition costs, net of tax of $2.8 million and $3.0 million, respectively and after-tax internal labor costs attributable to the acquisition of $1.2 million and $1.8 million, respectively. See Note 2 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.
[2]	Net income (loss) for the three and nine months ended September 30, 2015 included non-cash after-tax ceiling test impairments of $36 million and $113 million, respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.
[3]	Net income (loss) for the nine months ended September 30, 2015 included a non-cash after-tax impairment to equity investments of $3.4 million. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.

Business Segment Information_ S

Business Segment Information: Segment and Corporate Assets (Details) - USD ($) $ in Thousands		3 Months Ended					9 Months Ended
		Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		$ 4,246,562				$ 4,038,524	$ 4,246,562		$ 4,038,524	$ 4,245,902
Impairment of Oil and Gas Properties							183,565		0
Non-cash impairment of our Oil and Gas equity investments		0				0	5,170		0
Corporate activities[Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		130,321				105,322	130,321		105,322	106,605
Electric Utilities [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	[1]	2,846,931				2,671,601	2,846,931		2,671,601	2,748,680
Gas Utilities [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		831,802				827,069	831,802		827,069	906,922
Power Generation [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	[1]	78,666				64,359	78,666		64,359	76,945
Coal Mining [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		78,000				74,130	78,000		74,130	74,407
Oil and Gas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets		280,842	[2],[3]			$ 296,043	280,842	[2],[3]	$ 296,043	$ 332,343
Impairment of Oil and Gas Properties		$ 62,000		$ 94,000	$ 22,000		178,000
Non-cash impairment of our Oil and Gas equity investments							$ 5,200
[1]	The PPA under which Black Hills Colorado IPP provides generation to support Colorado Electric customers from the Pueblo Airport Generation Station is accounted for as a capital lease. As such, assets owned by our Power Generation segment are recorded at Colorado Electric under accounting for a capital lease.
[2]	As a result of continued low commodity prices during 2015, we recorded non-cash impairments of oil and gas assets included in our Oil and Gas segment of $62 million and $178 million for the for the three and nine months ended September 30, 2015, respectively. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.
[3]	Includes a non-cash impairment of our Oil and Gas equity investments of $5.2 million for the nine months ended September 30, 2015. See Note 17 to the Condensed Consolidated Financial Statements in this Quarterly Report on Form 10-Q.

Accounts Receivable_ Accounts46

Accounts Receivable: Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	$ (1,351)	$ (1,516)	$ (1,477)
Accounts receivable, net	115,502	189,992	123,399
Corporate[Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	0	0	0
Accounts receivable, net	1,566	2,555	1,459
Electric Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	(720)	(722)	(724)
Accounts receivable, net	77,686	85,466	74,478
Gas Utilities [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	(618)	(781)	(740)
Accounts receivable, net	27,871	92,159	35,887
Power Generation [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	0	0	0
Accounts receivable, net	1,186	1,369	1,368
Coal Mining [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	0	0	0
Accounts receivable, net	2,684	3,151	2,563
Oil and Gas [Member]
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	(13)	(13)	(13)
Accounts receivable, net	4,509	5,292	7,644
Billed Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	71,644	119,488	90,173
Billed Revenues [Member] | Corporate[Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	1,566	2,555	1,459
Billed Revenues [Member] | Electric Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	43,337	59,714	53,717
Billed Revenues [Member] | Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	18,349	47,394	23,409
Billed Revenues [Member] | Power Generation [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	1,186	1,369	1,368
Billed Revenues [Member] | Coal Mining [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	2,684	3,151	2,563
Billed Revenues [Member] | Oil and Gas [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	4,522	5,305	7,657
Unbilled Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	45,209	72,020	34,703
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	35,069	26,474	21,485
Unbilled Revenues [Member] | Gas Utilities [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	10,140	45,546	13,218
Unbilled Revenues [Member] | Power Generation [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] | Coal Mining [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	0	0	0
Unbilled Revenues [Member] | Oil and Gas [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	$ 0	$ 0	$ 0

Regulatory Accounting_ Regula47

Regulatory Accounting: Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets		$ 234,299	$ 257,839	$ 208,866
Regulatory Liabilities		$ 157,811	148,831	119,684
Deferred energy and gas costs
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		1 year
Regulatory Liabilities	[1],[2]	$ 9,899	6,496	5,535
Employee benefit plans
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		12 years
Regulatory Liabilities	[3],[4]	$ 53,140	53,139	34,409
Cost of removal
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		44 years
Regulatory Liabilities	[2]	$ 86,946	78,249	71,362
Other regulatory liabilities
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		25 years
Regulatory Liabilities	[3]	$ 7,826	10,947	8,378
Deferred energy and gas costs
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		1 year
Regulatory Assets	[1],[2]	$ 25,354	23,820	26,211
Deferred gas cost adjustments
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		2 years
Regulatory Assets	[1],[2]	$ 9,358	37,471	42,400
Gas price derivatives
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		7 years
Regulatory Assets	[2]	$ 23,681	18,740	7,470
AFUDC
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		45 years
Regulatory Assets	[5]	$ 12,580	12,358	12,411
Employee benefit plans
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		12 years
Regulatory Assets	[3],[4]	$ 95,779	97,126	64,908
Environmental
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	[2]	$ 1,209	1,314	1,314
Asset retirement obligations
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		44 years
Regulatory Assets	[2]	$ 675	3,287	3,282
Bond issue cost
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		23 years
Regulatory Assets	[2]	$ 3,169	3,276	3,311
Renewable energy standard adjustment
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		5 years
Regulatory Assets	[5]	$ 5,102	9,622	12,007
Flow through accounting
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		35 years
Regulatory Assets	[3]	$ 28,585	25,887	25,157
Decommissioning costs
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		10 years
Regulatory Assets	[6]	$ 16,353	12,484	0
Other regulatory assets
Schedule Of Regulatory Assets And Liabilities [Line Items]
Maximum Amortization Period		15 years
Regulatory Assets	[2]	$ 12,454	$ 12,454	$ 10,395
Black Hills Power [Member] | Decommissioning costs
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets	[6]	$ 13,000
[1]	Our deferred energy, fuel cost, and gas cost adjustments represent the cost of electricity and gas delivered to our electric and gas utility customers that is either higher or lower than current rates and will be recovered or refunded in future rates. Fluctuations in deferred gas cost adjustments compared to the same period in the prior year are primarily due to higher natural gas prices driven by demand and market conditions from the peak winter heating season in the first part of 2014. Our electric and gas utilities file periodic quarterly, semi-annual, and/or annual filings to recover these costs based on the respective cost mechanisms approved by their applicable state utility commissions.
[2]	Recovery of costs, but we are not allowed a rate of return.
[3]	In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base, respectively.
[4]	Increase compared to September 30, 2014 was driven by a decrease in the discount rate and a change in the mortality tables used in employee benefit plan estimates.
[5]	In addition to recovery of costs, we are allowed a rate of return.
[6]	Black Hills Power has approximately $13 million of decommissioning costs associated with the retirements of the Neil Simpson I and Ben French power plants that are allowed a rate of return, in addition to recovery of costs.

Materials, Supplies and Fuel_48

Materials, Supplies and Fuel: Materials, Supplies and Fuel (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Inventory, Net [Abstract]
Materials and supplies	$ 53,838	$ 49,555	$ 52,682
Fuel - Electric Utilities	6,139	6,637	7,108
Natural gas in storage held for distribution	30,372	34,999	45,936
Total materials, supplies and fuel	$ 90,349	$ 91,191	$ 105,726

Goodwill_ Goodwill (Details)

Goodwill: Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 353,396
Additions	6,131
Goodwill, ending balance	359,527
Electric Utilities [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	250,487
Additions	6,131	[1]
Goodwill, ending balance	256,618
Gas Utilities [Member]
Goodwill [Roll Forward]
Additions	0
Power Generation [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	8,765
Additions	0
Goodwill, ending balance	8,765
Aquila Transaction [Member] | Gas Utilities [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	94,144
Goodwill, ending balance	$ 94,144
[1]	Goodwill was recorded on the acquisition of Wyoming natural gas utility Energy West Wyoming, Inc., and natural gas pipeline assets from Energy West Development, Inc. completed on July 1, 2015.

Earnings Per Share_ Earnings 50

Earnings Per Share: Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income (loss) available for common stock	$ (9,943)	$ 27,363	$ (17,935)	$ 96,355
Weighted average shares - basic	44,635	44,415	44,598	44,382
Dilutive effect of:
Equity compensation	0	193	0	202
Weighted average shares - diluted	44,635	44,608	44,598	44,584

Earnings Per Share_ Anti-diluti

Earnings Per Share: Anti-dilutive shares (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities Excluded From Diluted Earnings Per Share Due to Net Loss	58,380		82,130
Anti-dilutive shares	121,000	99,000	114,000	75,000
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares	121,000	99,000	114,000	75,000

Notes Payable and Long-term D52

Notes Payable and Long-term Debt: Notes Payable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Revolving Credit Facility [Line Items]
Balance Outstanding	$ 117,900	$ 75,000	$ 184,000
Revolving Credit Facility [Member]
Revolving Credit Facility [Line Items]
Balance Outstanding	117,900	75,000	184,000
Letters of Credit	30,600	$ 35,000	$ 31,726
Current Borrowing Capacity	$ 500,000
Expiration Date	Jun. 26, 2020
Maximum Borrowing Capacity	$ 750,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.175%
Revolving Credit Facility [Member] | Base Rate [Member]
Revolving Credit Facility [Line Items]
Interest Rate at Period End	0.125%
Revolving Credit Facility [Member] | Eurodollar [Member]
Revolving Credit Facility [Line Items]
Interest Rate at Period End	1.125%
Revolving Credit Facility [Member] | Letter of Credit [Member]
Revolving Credit Facility [Line Items]
Interest Rate at Period End	1.125%

Notes Payable and Long-term D53

Notes Payable and Long-term Debt: Refinancing of Debt (Details) - Black Hills Corporation [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Corporate Term Loan Due June 2015 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 275
Corporate Term Loan Due April 2017 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis Spread on Variable Rate	0.90%
Corporate Debt Securities [Member] | Corporate Term Loan Due April 2017 [Member]
Debt Instrument [Line Items]
Additional debt used for general corporate purposes	$ 25
Corporate Debt Securities [Member] | Corporate Term Loan Due April 2017 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300
Debt Instrument, Maturity Date	Apr. 12, 2017

Notes Payable and Long-term D54

Notes Payable and Long-term Debt: Debt covenants (Details) - Revolving Credit Facility [Member] $ in Millions	Sep. 30, 2015USD ($)
Debt instrument, covenant, maximum Recourse Ratio	0.65
Recourse Leverage Ratio	58.00%
Source Gas [Member]
Debt instrument, covenant, maximum Recourse Ratio	0.65
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount	$ 1,460
Debt Instrument, Covenant, Trigger 1 [Member] | Source Gas [Member]
Debt instrument, covenant, maximum Recourse Ratio	0.70
Debt Instrument, Covenant, Trigger 2 [Member] | Source Gas [Member]
Debt instrument, covenant, maximum Recourse Ratio	0.75
Minimum [Member] | Source Gas [Member]
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount	$ 1,250
Maximum [Member] | Source Gas [Member]
Debt instrument, covenant, aggregate outstanding debt assumed or incurred, amount	$ 1,460

Risk Management Activities_ R55

Risk Management Activities: Risk Management Activities (Details) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2015USD ($)MMBTUbbl	Sep. 30, 2014USD ($)MMBTUbbl	Dec. 31, 2014USD ($)MMBTUbbl
Derivative [Line Items]
Derivative assets, current		$ 0	$ 0	$ 0
Derivative assets, non-current		0	0	0
Derivative liabilities, current		3,312	3,397	3,340
Derivative liabilities, non-current		722	3,273	2,680
Oil and Gas [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		8,800
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liabilities, current		3,312	3,397	3,340
Derivative liabilities, non-current		722	3,273	2,680
Notional Amount	[1]	$ 75,000	$ 75,000	$ 75,000
Weighted average fixed interest rate		4.97%	4.97%	4.97%
Maximum Term		1 year 4 months	2 years 3 months	2 years
Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net		$ (3,300)
Crude Oil [Member] | Swaps and Options [Member] | Oil and Gas [Member]
Derivative [Line Items]
Notional amount - commodities | bbl	[2]	258,000	391,500	334,500
Maximum Term Hedged in Cash Flow Hedge	[3]	1 month	1 month	1 month
Derivative assets, current		$ 0	$ 0	$ 0
Derivative assets, non-current		0	0	0
Derivative liabilities, current		0	0	0
Derivative liabilities, non-current		$ 0	$ 0	$ 0
Natural Gas [Member] | Swap [Member] | Oil and Gas [Member]
Derivative [Line Items]
Notional amount - commodities | MMBTU	[2]	5,392,500	7,930,000	6,582,500
Maximum Term Hedged in Cash Flow Hedge	[3]	1 month	1 month	1 month
Derivative assets, current		$ 0	$ 0	$ 0
Derivative assets, non-current		0	0	0
Derivative liabilities, current		0	0	0
Derivative liabilities, non-current		0	0	0
Utilities Group [Member] | Natural Gas, Distribution [Member]
Derivative [Line Items]
Derivative assets, current		0	0	0
Derivative assets, non-current		0	0	0
Derivative liabilities, non-current		0	0	0
Net Unrealized (Gain) Loss Included in Regulatory assets or Regulatory liabilities		$ 23,678	$ 7,470	$ 18,740
Utilities Group [Member] | Natural Gas, Distribution [Member] | Future [Member] | Purchase Contract [Member]
Derivative [Line Items]
Notional amount - commodities | MMBTU		17,180,000	16,290,000	19,370,000
Maximum Term	[4]	63 months	74 months	72 months
Utilities Group [Member] | Natural Gas, Distribution [Member] | Commodity Option [Member] | Purchase Contract [Member]
Derivative [Line Items]
Notional amount - commodities | MMBTU		6,300,000	7,070,000	4,020,000
Maximum Term	[4]	6 months	6 months	8 months
Utilities Group [Member] | Natural Gas, Distribution [Member] | Basis Swap [Member] | Purchase Contract [Member]
Derivative [Line Items]
Notional amount - commodities | MMBTU		12,980,000	12,025,000	12,005,000
Maximum Term	[4]	51 months	63 months	60 months
[1]	These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related borrowings.
[2]	Crude oil in Bbls, natural gas in MMBtus.
[3]	Refers to the tenor of the derivative instrument. Assets and liabilities are classified as current/non-current based on the production month hedged and the corresponding settlement of the derivative instrument.
[4]	Term reflects the maximum forward period hedged.

Risk Management Activities_ Hed

Risk Management Activities: Hedging Activities (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	$ 4,382	$ 4,985	$ 4,126	$ (1,653)
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	1,506	(2,060)	5,998	(5,442)
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	0	0	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	(898)	152	(2,674)	(277)
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	0	0	0	0
Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	(1,603)	(925)	(4,709)	(2,745)
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in AOCI Derivative (Effective Portion)	5,280	4,833	6,800	(1,376)
Commodity Contract [Member] | Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Reclassified Gain/(Loss) from AOCI into Income (Effective Portion)	3,109	(1,135)	10,707	(2,697)
Amount of Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion)	$ 0	$ 0	$ 0	$ 0

Fair Value Measurements_ Fair57

Fair Value Measurements: Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Fair Value, Transfers Between Level 1 and Level 2, Description and Policy [Abstract]
Assets-Transfers out of level 1 to 2	$ 0	$ 0	$ 0
Assets -Transfers out of level 2 to 1	0	0	0
Liabilities -Transfers out of level 1 to 2	0	0	0
Liabilities -Transfers out of level 2 to 1	0	0	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(14,387)	(17,546)	(5,896)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(24,912)	(19,776)	(10,031)
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 Assets, Total	0	0	0
Derivative Liabilities, Total	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]
Derivative Assets, Total	14,387	17,546	5,896
Derivative Liabilities, Total	28,946	25,796	16,701
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 Assets, Total	0	0	0
Derivative Liabilities, Total	0	0	0
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities, Fair Value Disclosure	4,034	6,020	6,670
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	0	0	0
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, Fair Value Disclosure	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, Fair Value Disclosure	4,034	6,020	6,670
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, Fair Value Disclosure	0	0	0
Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	0	0	0
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	0	0	0
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(6,642)	(8,599)	(322)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	0	0	(487)
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	6,642	8,599	322
Derivative Liabilities, Fair Value Disclosure	0	0	487
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	0	0	0
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	0	0	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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(4,622)	(6,558)	(1,545)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(467)	(473)	(865)
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	4,622	6,558	1,545
Derivative Liabilities, Fair Value Disclosure	467	473	865
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(3,123)	(2,389)	(4,029)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(24,445)	(19,303)	(8,679)
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	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, Commodity Derivatives	3,123	2,389	4,029
Derivative Liabilities, Fair Value Disclosure	24,445	19,303	8,679
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, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Total	0	0	0
Derivative Liabilities, Total	4,034	6,020	6,670
Estimate of Fair Value Measurement [Member] | Crude Oil [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Estimate of Fair Value Measurement [Member] | Crude Oil [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Estimate of Fair Value Measurement [Member] | Natural Gas [Member] | Commodity Option [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Estimate of Fair Value Measurement [Member] | Natural Gas [Member] | Basis Swap [Member] | Fair Value, Measurements, Recurring [Member] | Oil and Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	0	0	0
Estimate of Fair Value Measurement [Member] | Natural Gas, Distribution [Member] | Fair Value, Measurements, Recurring [Member] | Utilities Group [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0	0
Derivative Liabilities, Fair Value Disclosure	$ 0	$ 0	$ 0

Fair Value Measurements_ Balanc

Fair Value Measurements: Balance Sheet Location (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Designated as Hedging Instrument [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Net	$ 11,264	$ 15,157	$ 1,866
Derivative Liability, Fair Value, Net	4,501	6,493	8,023
Not Designated as Hedging Instrument [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Net	0	0	0
Derivative Liability, Fair Value, Net	21,322	16,914	4,650
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Assets, Current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	9,181	10,391	1,174
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Assets, Non-current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,083	4,766	692
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	375	185	497
Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Non-current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	92	288	856
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Assets, Current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0	0
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Assets, Non-current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0	0
Derivative Asset, Fair Value, Gross Liability	0	0	0
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	8,427	8,032	48
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, Non-current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	12,895	8,882	4,602
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	3,312	3,340	3,397
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, Non-current [Member]
Derivatives, Carrying Amount and Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Asset	0	0	0
Derivative Liability, Fair Value, Gross Liability	$ 722	$ 2,680	$ 3,273

Fair Value of Financial Instr59

Fair Value of Financial Instruments: Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		$ 38,841	$ 21,218	$ 11,939	$ 7,841
Restricted cash and equivalents		2,462	2,056	1,918
Notes payable		117,900	75,000	184,000
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		38,841	21,218	11,939
Restricted cash and equivalents		2,462	2,056	1,918
Notes payable		117,900	75,000	184,000
Long-term debt, including current maturities		1,567,797	1,542,589	1,382,519
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Fair Value	[1]	38,841	21,218	11,939
Restricted Cash Fair Value Disclosure	[1]	2,462	2,056	1,918
Notes payable, Fair Value	[1]	117,900	75,000	184,000
Long-term debt, including current maturities, Fair Value	[2]	$ 1,718,964	$ 1,734,555	$ 1,547,359
[1]	Carrying value approximates fair value due to either the short-term length of maturity or variable interest rates that approximate prevailing market rates, and therefore is classified in Level 1 in the fair value hierarchy.
[2]	Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy.

Other Comprehensive Income (L60

Other Comprehensive Income (Loss): Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 22,378	$ 17,919	$ 61,833	$ 53,665
Revenue	272,105	272,087	986,346	1,015,493
Utilities - Operating and maintenance	67,282	64,245	205,630	201,546
Non-regulated energy operations and maintenance	22,548	20,170	67,744	63,852
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	(21,978)	39,003	(27,061)	144,628
Income tax benefit (expense)	12,035	(11,640)	14,640	(48,272)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	(1,506)	2,060	(5,998)	5,442
Income tax benefit (expense)	558	(732)	2,548	(1,931)
Net income (loss) available for common stock	(948)	1,328	(3,450)	3,511
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [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	1,603	925	4,709	2,745
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Commodity Contract [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Revenue	(3,109)	1,135	(10,707)	2,697
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Utilities - Operating and maintenance	(26)	(26)	(80)	(77)
Non-regulated energy operations and maintenance	(29)	(22)	(86)	(93)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Utilities - Operating and maintenance	454	158	1,362	473
Non-regulated energy operations and maintenance	252	88	754	274
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before earnings (loss) of unconsolidated subsidiaries and income taxes	651	198	1,950	577
Income tax benefit (expense)	(228)	(69)	(684)	(202)
Net income (loss) available for common stock	$ 423	$ 129	$ 1,266	$ 375

Other Comprehensive Income (L61

Other Comprehensive Income (Loss): Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	$ (16,859)	$ (14,054)	$ (15,044)	$ (19,441)	$ (18,589)	$ (17,422)	$ (15,044)	$ (17,422)
Other comprehensive income (loss), net of tax	2,248	(2,805)	990	4,602	(852)	(1,167)	433	2,583
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(14,611)	(16,859)	(14,054)	(14,839)	(19,441)	(18,589)	(14,611)	(14,839)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	6,110	5,688	5,093	(9,167)	(8,611)	(7,133)	5,093	(7,133)
Other comprehensive income (loss), net of tax	1,825	422	595	4,473	(556)	(1,478)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	7,935	6,110	5,688	(4,694)	(9,167)	(8,611)	7,935	(4,694)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(22,969)	(19,742)	(20,137)	(10,274)	(9,978)	(10,289)	(20,137)	(10,289)
Other comprehensive income (loss), net of tax	423	(3,227)	395	129	(296)	311
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	$ (22,546)	$ (22,969)	$ (19,742)	$ (10,145)	$ (10,274)	$ (9,978)	$ (22,546)	$ (10,145)

Supplemental Disclosure of Ca62

Supplemental Disclosure of Cash Flow Information: Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Non-cash Investing and Financing Activities from Continuing Operations [Abstract]
Property, plant and equipment acquired with accrued liabilities	$ 52,314	$ 52,484
Increase (decrease) in capitalized assets associated with asset retirement obligations	0	(2,785)
Supplemental Cash Flow Elements [Abstract]
Interest (net of amounts capitalized)	(49,797)	(46,086)
Income taxes, net	$ (1,202)	$ (396)

Employee Benefit Plans_ Emplo63

Employee Benefit Plans: Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 1,494	$ 1,362	$ 4,482	$ 4,086
Interest cost	3,880	3,963	11,640	11,889
Expected return on plan assets	(4,867)	(4,516)	(14,601)	(13,549)
Prior service cost (benefit)	15	16	45	47
Net loss (gain)	2,759	1,201	8,277	3,604
Net periodic benefit cost	3,281	2,026	9,843	6,077
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	10,200		10,200
Estimated Future Employer Contributions in Current Fiscal Year			0
Estimated Future Employer Contributions in Next Fiscal Year			10,200
Defined Benefit Postretirement Healthcare Plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	464	425	1,392	1,275
Interest cost	450	480	1,350	1,439
Expected return on plan assets	(33)	(21)	(99)	(64)
Prior service cost (benefit)	(107)	(107)	(321)	(321)
Net loss (gain)	102	40	306	120
Net periodic benefit cost	876	817	2,628	2,449
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	939		2,817
Estimated Future Employer Contributions in Current Fiscal Year			939
Estimated Future Employer Contributions in Next Fiscal Year			4,026
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	(84)	374	799	1,123
Interest cost	364	362	1,092	1,085
Prior service cost (benefit)	1	1	3	2
Net loss (gain)	270	124	810	373
Net periodic benefit cost	551	$ 861	2,704	$ 2,583
Pension and Other Postretirement Benefit Contributions [Abstract]
Contributions by Employer	$ 372		1,116
Estimated Future Employer Contributions in Current Fiscal Year			372
Estimated Future Employer Contributions in Next Fiscal Year			$ 1,544

Commitments and Contingencies_

Commitments and Contingencies: Commitments and Contingencies - Oil Creek Fire (Details) - Pending Litigation [Member] - Oil Creek Fire [Member] - Loss from Catastrophes [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Minimum [Member]
Loss Contingencies [Line Items]
Insurance Coverage Deductible Per Occurrence	$ 1
Maximum [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	$ 55

Commitments and Contingencies65

Commitments and Contingencies: Commitments and Contingencies - Dividend Restrictions (Details) $ in Millions	Sep. 30, 2015USD ($)
Utilities Group [Member]
Related Party Transaction [Line Items]
Restricted Net Assets for Subsidiaries	$ 334

Impairment of Assets_ Impairmen

Impairment of Assets: Impairment of Long-lived assets (Details) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015$ / bbl$ / MMcf	Jun. 30, 2015$ / bbl$ / MMcf	Mar. 31, 2015$ / bbl$ / MMcf
Impairment of Oil and Gas Properties | $				$ 183,565	$ 0
Oil and Gas [Member]
Impairment of Oil and Gas Properties | $	$ 62,000	$ 94,000	$ 22,000	$ 178,000
Average Natural Gas Price Per MCF, NYMEX						3.06	3.39	3.88
Average Natural Gas Price Per MCF, Wellhead						1.72	2.14	2.69
Average Crude Oil Price, Per Barrel, NYMEX | $ / bbl						59.21	71.68	82.72
Average Crude Oil Price Per Barrel, Wellhead | $ / bbl						52.82	63.76	74.13

Impairment of Assets_ Equity in

Impairment of Assets: Equity investments in unconsolidated subsidiaries (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Non-cash impairment of our Oil and Gas equity investments	$ 0	$ 0	$ 5,170	$ 0
Oil and Gas [Member]
Non-cash impairment of our Oil and Gas equity investments			$ 5,200
Willow Creek / Lodge Creek Pipeline and Gathering System [Member] | Oil and Gas [Member]
Equity Method Investment, Ownership Percentage	25.00%		25.00%

Income Taxes_ Income Taxes (Det

Income Taxes: Income Taxes (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Federal statutory rate	(35.00%)	35.00%	(35.00%)	35.00%
State income tax (net of federal tax effect)	(4.70%)	(0.20%)	(6.70%)	0.70%
Percentage depletion in excess of cost	(2.00%)	(1.30%)	(4.50%)	(1.00%)
Accounting for uncertain tax positions adjustment	1.20%	(2.90%)	4.70%	(0.40%)
Flow-through adjustments	(2.40%)	(1.70%)	(4.70%)	(1.10%)
Inter-period tax allocation	(11.20%)	1.60%
Other tax differences	(0.70%)	(0.70%)	1.30%	0.10%
Effective Tax Rate	(54.80%)	29.80%	(44.90%)	33.30%

Subsequent Event_ Build Transfe

Subsequent Event: Build Transfer Agreement (Details) $ in Millions	Nov. 02, 2015USD ($)
Subsequent Event [Member]
Subsequent Event [Line Items]
Build/Transfer Agreement - Peak View wind project	$ 109

Subsequent Event_ Interest Rate

Subsequent Event: Interest Rate Swap Lock (Details) - Designated as Hedging Instrument [Member] - Interest Rate Swap [Member] - USD ($) $ in Millions		Oct. 02, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Derivative, notional amount	[1]		$ 75	$ 75	$ 75
Weighted average fixed interest rate			4.97%	4.97%	4.97%
Subsequent Event [Member]
Derivative, notional amount		$ 250
Weighted average fixed interest rate		2.29%
[1]	These swaps are designated to borrowings on our Revolving Credit Facility, and are priced using three-month LIBOR, matching the floating portion of the related borrowings.