Energen (EGN) 10-Q 7 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 31, 2014
Document and Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'ENERGEN CORP	'
Entity Central Index Key	'0000277595	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	73,203,569

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$1,321	$2,523
Short-term investments	18,000	0
Accounts receivable, net of allowance for doubtful accounts of $681 and $696 at September 30, 2014 and December 31, 2013, respectively	185,342	136,334
Inventories	14,373	11,130
Assets held for sale with prior period comparable	0	1,242,872
Deferred income taxes	8,085	21,250
Derivative instruments	30,195	17,463
Prepayments and other	31,205	9,989
Total current assets	288,521	1,441,561
Oil and natural gas properties, successful efforts method	'	'
Proved properties	7,635,488	6,695,400
Unproved properties	158,500	168,975
Less accumulated depreciation, depletion and amortization	2,336,114	1,776,802
Oil and natural gas properties, net	5,457,874	5,087,573
Other property and equipment, net	43,355	30,515
Total property, plant and equipment, net	5,501,229	5,118,088
Other Assets	'	'
Other postretirement assets	4,566	8,894
Noncurrent derivative instruments	5,758	5,439
Other assets	32,896	48,230
TOTAL ASSETS	5,832,970	6,622,212
Current Liabilities	'	'
Long-term debt due within one year	0	60,000
Notes payable to banks	0	489,000
Accounts payable	110,955	78,178
Accrued taxes	227,180	8,201
Accrued wages and benefits	39,515	27,036
Accrued capital costs	131,792	93,623
Revenue and royalty payable	65,271	51,519
Liabilities related to assets held for sale with prior period comparable	0	831,570
Derivative instruments	808	30,302
Other	17,917	21,796
Total current liabilities	593,438	1,691,225
Deferred Credits and Other Liabilities	'	'
Long-term debt	632,458	1,093,541
Asset retirement obligations	115,431	108,533
Pension liabilities	41,264	47,484
Deferred income taxes	1,074,690	807,614
Noncurrent derivative instruments	640	398
Other long-term liabilities	13,801	15,398
Total liabilities	2,471,722	3,764,193
Commitments and Contingencies	'	'
Shareholders’ Equity	'	'
Preferred stock, cumulative, $0.01 par value, 5,000,000 shares authorized	0	0
Common shareholders’ equity	'	'
Common stock, $0.01 par value; 150,000,000 shares authorized; 76,098,344 shares and 75,574,156 shares issued at September 30, 2014 and December 31, 2013, respectively	761	756
Premium on capital stock	561,826	523,711
Retained earnings	2,946,390	2,476,616
Accumulated other comprehensive income (loss), net of tax	'	'
Unrealized gain on hedges, net	3,618	13,362
Pension and postretirement plans	-26,313	-32,245
Interest rate swap	0	-1,184
Deferred compensation plan	3,320	3,259
Treasury stock, at cost; 2,986,201 shares and 2,967,999 shares at September 30, 2014 and December 31, 2013, respectively	-128,354	-126,256
Total shareholders’ equity	3,361,248	2,858,019
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$5,832,970	$6,622,212

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Current Assets	'	'
Allowance for doubtful accounts	$681	$696
Shareholders’ Equity	'	'
Preferred stock, par value	$0.01	$0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	76,098,344	75,574,156
Treasury stock, shares	2,986,201	2,967,999

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues	'	'	'	'
Oil, natural gas liquids and natural gas sales	$350,773	$360,507	$1,057,447	$927,746
Gain (loss) on derivative instruments, net	147,735	-88,192	9,498	-51,904
Loss on sale of assets and other	-747	-277	-1,809	-492
Total revenues	497,761	272,038	1,065,136	875,350
Operating Costs and Expenses	'	'	'	'
Oil, natural gas liquids and natural gas production	67,720	65,795	199,861	190,944
Production and ad valorem taxes	25,729	22,230	81,102	69,109
Depreciation, depletion and amortization	139,104	124,911	399,568	332,247
Asset impairment	179,074	0	179,074	0
Exploration	8,255	8,949	23,644	13,902
General and administrative	27,784	30,947	93,499	86,699
Accretion of discount on asset retirement obligations	1,924	1,771	5,650	5,187
Total costs and expenses	449,590	254,603	982,398	698,088
Operating Income	48,171	17,435	82,738	177,262
Other Income (Expense)	'	'	'	'
Interest expense	-11,522	-10,149	-27,374	-30,232
Other income	37	1,249	1,047	2,619
Total other expense	-11,485	-8,900	-26,327	-27,613
Income From Continuing Operations Before Income Taxes	36,686	8,535	56,411	149,649
Income tax expense	16,055	3,128	23,287	53,401
Income From Continuing Operations	20,631	5,407	33,124	96,248
Discontinued Operations, net of tax	'	'	'	'
Income (loss) from discontinued operations	-3,485	-9,027	30,435	39,891
Gain (loss) on disposal of discontinued operations	440,105	-15,678	439,055	-15,678
Income (Loss) From Discontinued Operations	436,620	-24,705	469,490	24,213
Net Income (Loss)	$457,251	($19,298)	$502,614	$120,461
Diluted Earnings Per Average Common Share	'	'	'	'
Continuing operations (in dollars per share)	$0.28	$0.07	$0.45	$1.33
Discontinued operations (in dollars per share)	$5.94	($0.34)	$6.41	$0.34
Net Income (Loss) (in dollars per share)	$6.22	($0.27)	$6.86	$1.67
Basic Earnings Per Average Common Share	'	'	'	'
Continuing Operations (in dollars per share)	$0.28	$0.07	$0.45	$1.33
Discontinued operations (in dollars per share)	$5.98	($0.34)	$6.45	$0.34
Net Income (Loss) (in dollars per share)	$6.26	($0.27)	$6.90	$1.67
Dividends Per Common (In dollar per shares)	$0.15	$0.14	$0.45	$0.44
Diluted Shares Outstanding (in shares)	73,507	72,346	73,238	72,272
Basic Shares Outstanding (in shares)	73,093	72,346	72,861	72,220

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income (Loss)	$457,251	($19,298)	$502,614	$120,461
Other comprehensive income (loss):	'	'	'	'
Total cash flow hedges	-3,525	-5,220	-8,560	-28,831
Pension and postretirement plans:	'	'	'	'
Amortization of net benefit obligation at transition, net of tax of ($1), $26, $6 and $77, respectively	-1	48	11	143
Amortization of prior service cost, net of tax of $26, $28, $78 and $82, respectively	48	51	144	153
Amortization of net loss, including settlement charges, net of tax of $500, $729, $4,071 and $2,383, respectively	930	1,354	7,561	4,425
Current period change in fair value of pension and postretirement plans, net of tax of $190, $2,238, ($962) and $2,238, respectively	352	4,157	-1,784	4,157
Total pension and postretirement plans	1,329	5,610	5,932	8,878
Comprehensive Income (Loss)	455,055	-18,908	499,986	100,508
Commodity contracts	'	'	'	'
Other comprehensive income (loss):	'	'	'	'
Current period change in fair value of derivative commodity instruments, net of tax of $18, $42, $25, and ($6,669), respectively	29	69	40	-10,882
Reclassification adjustment for derivative commodity instruments, net of tax of ($2,277), ($3,205), ($5,997) and ($11,486), respectively	-3,715	-5,229	-9,784	-18,740
Current period change in fair value of interest rate swap, net of tax of $0, ($188), ($160) and ($23), respectively	29	69	40	-10,882
Reclassification adjustment for interest rate swap, net of tax of $86, $156, $798 and $449, respectively	-3,715	-5,229	-9,784	-18,740
Interest rate swap	'	'	'	'
Other comprehensive income (loss):	'	'	'	'
Current period change in fair value of derivative commodity instruments, net of tax of $18, $42, $25, and ($6,669), respectively	0	-350	-298	-42
Reclassification adjustment for derivative commodity instruments, net of tax of ($2,277), ($3,205), ($5,997) and ($11,486), respectively	161	290	1,482	833
Current period change in fair value of interest rate swap, net of tax of $0, ($188), ($160) and ($23), respectively	0	-350	-298	-42
Reclassification adjustment for interest rate swap, net of tax of $86, $156, $798 and $449, respectively	$161	$290	$1,482	$833

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Amortization of net obligation at transition, tax	($1)	$26	$6	$77
Amortization of prior service cost, tax	26	28	78	82
Amortization of net loss, including settlement charges, tax	500	729	4,071	2,383
Current period change in fair value of pension, tax	190	2,238	-962	2,238
Commodity contracts	'	'	'	'
Current period change in fair value of interest rate swap, tax	18	42	25	-6,669
Reclassification adjustment for derivative instruments, tax	-2,277	-3,205	-5,997	-11,486
Interest rate swap	'	'	'	'
Current period change in fair value of interest rate swap, tax	0	-188	-160	-23
Reclassification adjustment for derivative instruments, tax	$86	$156	$798	$449

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Statement of Cash Flows [Abstract]	'	'
Cash and cash equivalents	$1,321	$12,413
Operating Activities	'	'
Net Income (Loss)	502,614	120,461
Income from discontinued operations	-469,490	-24,213
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	399,568	332,247
Asset impairment	179,074	0
Accretion of discount on asset retirement obligations	5,650	5,187
Deferred income taxes	287,855	58,665
Change in derivative fair value	-53,928	53,581
(Gain) loss on sale of assets	105	-91
Stock-based compensation expense	10,837	11,200
Exploration, including dry holes	10,808	8,759
Discontinued operations	112,180	149,462
Other, net	-1,972	10,013
Net change in:	'	'
Accounts receivable	-28,486	31,051
Inventories	-3,243	7,836
Accounts payable	27,967	-58,003
Income taxes	-266,229	16,061
Pension and other postretirement benefit contributions	-2,397	-5,484
Other current assets and liabilities	-1,625	11,284
Net cash provided by operating activities	709,288	728,016
Investing Activities	'	'
Additions to oil and natural gas properties	-906,166	-894,713
Acquisitions, net of cash acquired	-26,371	-21,400
Proceeds from sale of Alabama Gas Corporation and other assets	1,347,904	2,382
Purchase of short-term investments	-377,000	0
Sale of short-term investments	359,000	0
Discontinued operations	-51,850	-54,052
Other, net	0	-405
Net cash provided by (used in) investing activities	345,517	-968,188
Financing Activities	'	'
Payment of dividends on common stock	-32,840	-31,454
Issuance of common stock	23,053	13,680
Reduction of long-term debt	-600,000	0
Payment of debt issuance costs	-7,912	0
Net change in credit facility	-410,100	286,000
Tax benefit on stock compensation	3,873	2,710
Discontinued operations	-35,113	-28,055
Net cash provided by (used in) financing activities	-1,059,039	242,881
Net increase (decrease) in cash and cash equivalents	-4,234	2,709
Cash and cash equivalents at beginning of period	$5,555	$9,704

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and Basis of Presentation	'
	ORGANIZATION AND BASIS OF PRESENTATION
	Energen Corporation (Energen or the Company) is an oil and natural gas exploration and production company primarily engaged in the exploration, development and production of oil and gas properties in the Permian Basin in west Texas and in the San Juan Basin in New Mexico and Colorado in the continental United States. Our operations are conducted substantially through our subsidiary Energen Resources Corporation (Energen Resources). The unaudited consolidated financial statements and notes should be read in conjunction with the financial statements and notes thereto for the years ended December 31, 2013, 2012 and 2011, included in the 2013 Annual Report of Energen and Alabama Gas Corporation (Alagasco) on Form 10-K.
	Prior to September 2, 2014, Energen owned Alagasco, which was engaged in the purchase, distribution and sale of natural gas principally in central and north Alabama. On September 2, 2014, Energen completed the transaction to sell Alagasco to The Laclede Group, Inc. (Laclede) for $1.6 billion, less the assumption of $267 million in debt. The net pre-tax proceeds to Energen totaled approximately $1.32 billion, subject to closing adjustments. This sale had an effective date of August 31, 2014. Energen used cash proceeds from the sale to reduce long-term and short-term indebtedness. During the second quarter of 2014, Energen classified Alagasco as held for sale with prior period comparable and reflected the associated operating results in discontinued operations. See Note 12, Discontinued Operations, for further information regarding the sale of Alagasco.
	Our accompanying unaudited consolidated financial statements include Energen and its subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the disclosures required for complete financial statements. Results of operations for interim periods are not necessarily indicative of the results that may be expected for the year. In the opinion of management, the accompanying financial statements reflect all adjustments necessary to present fairly our financial position, results of operations, and cash flows for the periods and as of the dates shown. Such adjustments consist of normal recurring items. In addition, and in connection with the sale of Alagasco, we have chosen to reformat our financial statements to reflect a presentation more closely aligned with our peers in the oil and natural gas industry. As part of the financial statement reformatting, certain reclassifications were made to conform prior periods’ financial statements to the current-quarter presentation. These reclassifications primarily included further detail under operating costs and expenses. We further reclassified all commodity hedges from oil and natural gas operating revenues to gain (loss) on derivative instruments, net, as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Open non-cash mark-to-market gains (losses) on derivative instruments	$	147,287		$	(63,560	)	$	53,985		$	(48,459	)
	Closed gains (losses) on derivative instruments	448			(24,632		)	(44,487		)	(3,445		)
	Gain (loss) on derivative instruments, net	$	147,735		$	(88,192	)	$	9,498		$	(51,904	)
	We classified as discontinued operations interest on debt required to be extinguished, certain depreciation costs that ended at close, the related income tax impact of these items and the earnings of Alagasco. In addition, we reclassified from discontinued operations certain general and administrative costs, other income and the related tax impact from these items. The table below provides a detail of these items included in income (loss) from discontinued operations at September 30, 2014:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Alagasco net income (loss)	$	(1,767	)	$	(8,961	)	$	40,646		$	37,557
	Depreciation, depletion and amortization	(103		)	(150		)	(408		)	(443		)
	General and administrative	1,710			1,158			3,337			4,784
	Interest expense	(4,329		)	(3,676		)	(17,306		)	(9,786		)
	Other income	—			(409		)	(347		)	(882		)
	Income tax expense	1,029			1,145			5,567			2,392
	Alagasco income (loss) from discontinued operations	(3,460		)	(10,893		)	31,489			33,622
	Energen income (loss) from discontinued operations	(25		)	1,866			(1,054		)	6,269
	Income (loss) from discontinued operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891

Derivative_Commodity_Instrumen

Derivative Commodity Instruments	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Commodity Instruments	'
	DERIVATIVE COMMODITY INSTRUMENTS
	We periodically enter into derivative commodity instruments to hedge our exposure to price fluctuations on oil, natural gas liquids and natural gas production. Such instruments may include over-the-counter (OTC) swaps and basis swaps typically executed with investment and commercial banks and energy-trading firms. Derivative transactions are pursuant to standing authorizations by the Board of Directors, which do not authorize speculative positions.
	Due to the volatility of commodity prices, the estimated fair value of our derivative instruments is subject to fluctuation from period to period, which could result in significant differences between the current estimated fair value and the ultimate settlement price. Additionally, Energen is at risk of economic loss based upon the creditworthiness of our counterparties. We were in a net gain position with thirteen of our active counterparties and in a net loss position with the remaining one at September 30, 2014. The largest counterparty net gain positions at September 30, 2014, J.P. Morgan Ventures Energy Corporation, J Aron & Company and Bank of Montreal, constituted approximately $8.5 million, $4.4 million and $3.7 million, respectively, of Energen’s total gain on fair value of derivatives.
	Prior to June 30, 2013, Energen used cash flow hedge accounting where applicable for its derivative transactions. The effective portion of the gain or loss on the derivative instrument was recognized in accumulated other comprehensive income as a component of shareholders’ equity and subsequently reclassified as gain (loss) on derivative instruments, net when the forecasted transaction affected earnings. The ineffective portion of a derivative’s change in fair value was required to be recognized immediately in gain (loss) on derivative instruments, net. All other derivative transactions not designated as cash flow hedge accounting are accounted for as mark-to-market transactions with gains or losses recognized in the period of change in gain (loss) on derivative instruments, net.
	Effective March 31, 2013 and June 30, 2013, Energen dedesignated from cash flow hedge accounting 5,078 thousand barrels (MBbl) and 2,353 MBbl, respectively, of various New York Mercantile Exchange (NYMEX) oil contracts associated with the Permian Basin due to lack of correlation. Gains and losses from inception of the hedge to the dedesignation date were frozen in accumulated other comprehensive income until the forecasted transactions actually occurred. Subsequent gains or losses will be accounted for as mark-to-market transactions and recognized immediately through gain (loss) on derivative instruments, net.
	Effective June 30, 2013, Energen elected to discontinue the use of cash flow hedge accounting and to dedesignate all remaining derivative commodity instruments that were previously designated as cash flow hedges. As a result of discontinuing hedge accounting, any gains or losses from inception of the hedge to June 30, 2013 were frozen in accumulated other comprehensive income until the forecasted transactions actually occurred. Any subsequent gains or losses will be accounted for as mark-to-market and recognized immediately through gain (loss) on derivative instruments, net. As a result of Energen’s election to discontinue hedge accounting, all derivative transactions entered into subsequent to June 30, 2013 will be accounted for as mark-to-market transactions with gains or losses recognized in the period of change in gain (loss) on derivative instruments, net.
	The following tables detail the offsetting of derivative assets and liabilities as well as the fair values of derivatives on the balance sheets:
	(in thousands)	30-Sep-14
											Gross Amounts Not Offset in the Balance Sheets
		Gross Amounts Recognized at Fair Value			Gross Amounts Offset in the Balance Sheets			Net Amount Presented in the Balance Sheets			Financial Instruments		Cash Collateral Received		Net Fair Value Presented in the Balance Sheets
	Derivatives not designated as hedging instruments
	Assets
	Derivative instruments	$	37,039		$	(6,844	)	$	30,195		$	—	$	—	$	30,195
	Noncurrent derivative instruments	6,581			(823		)	5,758			—		—		5,758
	Total derivative assets	43,620			(7,667		)	35,953			—		—		35,953
	Liabilities
	Derivative instruments	7,652			(6,844		)	808			—		—		808
	Noncurrent derivative instruments	1,463			(823		)	640			—		—		640
	Total derivative liabilities	9,115			(7,667		)	1,448			—		—		1,448
	Total derivatives	$	34,505		$	—		$	34,505		$	—	$	—	$	34,505
	(in thousands)	31-Dec-13
											Gross Amounts Not Offset in the Balance Sheets
		Gross Amounts Recognized at Fair Value			Gross Amounts Offset in the Balance Sheets			Net Amount Presented in the Balance Sheets			Financial Instruments		Cash Collateral Received		Net Fair Value Presented in the Balance Sheets
	Derivatives not designated as hedging instruments
	Assets
	Derivative instruments	$	36,223		$	(18,760	)	$	17,463		$	—	$	—	$	17,463
	Noncurrent derivative instruments	7,992			(2,553		)	5,439			—		—		5,439
	Total derivative assets	44,215			(21,313		)	22,902			—		—		22,902
	Liabilities
	Derivative instruments	49,062			(18,760		)	30,302			—		—		30,302
	Noncurrent derivative instruments	2,553			(2,553		)	—			—		—		—
	Total derivative liabilities	51,615			(21,313		)	30,302			—		—		30,302
	Total derivatives	$	(7,400	)	$	—		$	(7,400	)	$	—	$	—	$	(7,400	)
	Energen had a net $2.2 million and a net $8.2 million deferred tax liability included in current deferred income taxes on the balance sheets related to derivative items included in accumulated other comprehensive income as of September 30, 2014, and December 31, 2013, respectively.
	The following tables detail the effect of derivative commodity instruments in cash flow hedging relationships on the financial statements:
	(in thousands)	Location on Statements of Income	Three months			Three months
			ended			ended
			30-Sep-14			30-Sep-13
	Net gain recognized in other comprehensive income on derivatives (effective portion), net of tax of $18 and $42	—	$	29		$	69
	Gain reclassified from accumulated other comprehensive income into income (effective portion)	Gain (loss) on derivative instruments, net	$	5,992		$	8,455
	Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	Gain (loss) on derivative instruments, net	$	—		$	(22	)
	(in thousands)	Location on Statements of Income	Nine months			Nine months
			ended			ended
			30-Sep-14			30-Sep-13
	Net gain (loss) recognized in other comprehensive income on derivatives (effective portion), net of tax of $25 and ($6,669)	—	$	40		$	(10,882	)
	Gain reclassified from accumulated other comprehensive income into income (effective portion)	Gain (loss) on derivative instruments, net	$	15,781		$	29,391
	Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	Gain (loss) on derivative instruments, net	$	—		$	835
	The following tables detail the effect of open and closed derivative commodity instruments not designated as hedging instruments on the income statement:
	(in thousands)	Location on Statements of Income	Three months			Three months
			ended			ended
			30-Sep-14			30-Sep-13
	Gain (loss) recognized in income on derivatives	Gain (loss) on derivative instruments, net	$	141,743		$	(92,313	)
	(in thousands)	Location on Statements of Income	Nine months			Nine months
			ended			ended
			30-Sep-14			30-Sep-13
	Loss recognized in income on derivatives	Gain (loss) on derivative instruments, net	$	(6,283	)	$	(70,735	)
	As of September 30, 2014, $3.6 million, net of tax, of deferred net gains on derivative instruments recorded in accumulated other comprehensive income are expected to be reclassified and reported in earnings as revenues during the next twelve-month period. During 2013, we had a discontinuance of hedge accounting when Energen determined it was probable certain forecasted volumes would not occur due to certain properties being sold. This discontinuance of hedge accounting resulted in $1.7 million of after-tax losses being recognized into gain (loss) on derivative instruments, net during the nine months ended September 30, 2014.
	As of September 30, 2014, Energen had entered into the following transactions for the remainder of 2014 and subsequent years:
	Production Period	Total Hedged Volumes		Average Contract	Description
				Price
	Oil
	2014	2,502	MBbl	$92.66 Bbl	NYMEX Swaps
	2015	8,280	MBbl	$89.30 Bbl	NYMEX Swaps
Oil Basis Differential
2014	300	MBbl	$(3.30) Bbl	WTS/WTI Basis Swaps*
2014	600	MBbl	$(3.08) Bbl	WTI/WTI Basis Swaps**
2015	2,160	MBbl	$(4.30) Bbl	WTS/WTI Basis Swaps*
2015	6,120	MBbl	$(5.11) Bbl	WTI/WTI Basis Swaps**
Natural Gas Liquids
2014	18.5	MMgal	$0.93 Gal	Liquids Swaps
Natural Gas
2014	2.6	Bcf	$4.57 Mcf	NYMEX Swaps
2014	7.6	Bcf	$4.62 Mcf	Basin Specific Swaps - San Juan
2014	2.6	Bcf	$3.81 Mcf	Basin Specific Swaps - Permian
2015	23	Bcf	$4.13 Mcf	Basin Specific Swaps - San Juan
2015	6	Bcf	$4.20 Mcf	Basin Specific Swaps - Permian
Natural Gas Basis Differential
2014	1.5	Bcf	$(0.09) Mcf	San Juan Basis Swaps
2014	0.6	Bcf	$(0.17) Mcf	Permian Basis Swaps
*WTS - West Texas Sour/Midland, WTI - West Texas Intermediate/Cushing
**WTI - West Texas Intermediate/Midland, WTI - West Texas Intermediate/Cushing
As of September 30, 2014, the maximum term over which Energen has hedged exposures to the variability of cash flows is through December 31, 2015.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	FAIR VALUE MEASUREMENTS
	Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). In determining fair value, we use various valuation approaches and classify all assets and liabilities based on the lowest level of input that is significant to the fair value measurement. Observable inputs represent market data obtained from independent sources, whereas unobservable inputs reflect our own considerations about the assumptions other market participants would use in pricing the asset or liability based on the best information available in the circumstances. Assessing the significance of a particular input may require judgment considering factors specific to the asset or liability, and may affect the valuation of the asset or liability and its placement within the fair value hierarchy. The hierarchy is broken down into three levels based on the observability of inputs as follows:
	Level 1 -	Unadjusted quoted prices in active markets for identical assets or liabilities;
	Level 2 -	Pricing inputs other than quoted prices in active markets included within Level 1, which are either directly or indirectly observable through correlation with market data as of the reporting date;
	Level 3 -	Pricing that requires inputs that are both significant and unobservable to the calculation of the fair value measure. The fair value measure represents estimates of the assumptions that market participants would use in pricing the asset or liability. Unobservable inputs are developed based on the best available information and subject to cost-benefit constraints.
	No transfers between fair value hierarchy levels occurred during the three months or nine months ended September 30, 2014 or 2013.
	Assets and Liabilities Measured at Fair Value on a Recurring Basis
	Energen classifies the fair value of multiple derivative instruments executed under master netting arrangements as net derivative assets and liabilities. The following fair value hierarchy tables present information about Energen’s assets and liabilities measured at fair value on a recurring basis:
		September 30, 2014
	(in thousands)	Level 2			Level 3			Total
	Assets:
	Derivative instruments	$	16,355		$	13,840		$	30,195
	Noncurrent derivative instruments	4,763			995			5,758
	Total assets	21,118			14,835			35,953
	Liabilities:
	Derivative instruments	(1,499		)	691			(808		)
	Noncurrent derivative instruments	—			(640		)	(640		)
	Total liabilities	(1,499		)	51			(1,448		)
	Net derivative asset	$	19,619		$	14,886		$	34,505
		31-Dec-13
	(in thousands)	Level 2			Level 3			Total
	Assets:
	Derivative instruments	$	(1,658	)	$	19,121		$	17,463
	Noncurrent derivative instruments	4,383			1,056			5,439
	Total assets	2,725			20,177			22,902
	Liabilities:
	Derivative instruments	(28,414		)	(1,888		)	(30,302		)
	Total liabilities	(28,414		)	(1,888		)	(30,302		)
	Net derivative asset (liability)	$	(25,689	)	$	18,289		$	(7,400	)
	Derivative Instruments: The fair value of Energen’s derivative commodity instruments is determined using market transactions and other market evidence whenever possible, including market-based inputs to models and broker or dealer quotations. Our OTC derivative contracts trade in less liquid markets with limited pricing information as compared to markets with actively traded, unadjusted quoted prices; accordingly, the determination of fair value is inherently more difficult. OTC derivatives for which we are able to substantiate fair value through directly observable market prices are classified within Level 2 of the fair value hierarchy. These Level 2 fair values consist of swaps priced in reference to NYMEX oil and natural gas prices. OTC derivatives valued using unobservable market prices have been classified within Level 3 of the fair value hierarchy. These Level 3 fair values include basin specific, basis and natural gas liquids swaps. We consider the frequency of pricing and variability in pricing between sources in determining whether a market is considered active. While Energen does not have access to the specific assumptions used in its counterparties’ valuation models, Energen maintains communications with its counterparties and discusses pricing practices. Further, we corroborate the fair value of our transactions by comparison of market-based price sources.
	Energen utilizes a discounted cash flow model in valuing its interest rate derivatives, which are comprised of interest rate swap agreements. The fair value attributable to Energen's interest rate derivative contracts is based on (i) the contracted notional amounts, (ii) active market-quoted London Interbank Offered Rate (LIBOR) yield curves and (iii) the applicable credit-adjusted risk-free rate yield curve.
	At September 30, 2014, Energen had interest rate swap agreements with a notional of $150 million. The interest rate swaps exchange a variable interest rate for a fixed interest rate of 1.0425 percent. The fair value of our interest rate swaps was a $1.0 million and a $1.8 million liability at September 30, 2014 and December 31, 2013, respectively, and are classified as Level 2 fair value liabilities. The fair value of our interest rate swaps are recognized on a gross basis in accounts payable on the balance sheets.
	Level 3 Fair Value Instruments: Energen prepared a sensitivity analysis to evaluate the hypothetical effect that changes in the prices used to estimate fair value would have on the fair value of its Level 3 instruments. We estimate that a 10 percent increase or decrease in commodity prices would result in an approximate $13 million change in the fair value of open Level 3 derivative contracts. The resulting impact upon the results of operations would be an approximate $13 million associated with open Level 3 derivative contracts. Liquidity requirements to meet the obligation would not be significantly impacted as gains and losses on the derivative contracts would be similarly offset by physical sales at the spot market price.
	The tables below set forth a summary of changes in the fair value of Energen’s Level 3 derivative commodity instruments as follows:
		Three months ended			Three months ended
	(in thousands)	September 30, 2014			September 30, 2013
	Balance at beginning of period	$	5,207		$	51,131
	Realized gains	10,769			10,852
	Unrealized gains (losses) relating to instruments held at the reporting date*	9,348			(10,947		)
	Settlements during period	(10,438		)	(9,830		)
	Balance at end of period	$	14,886		$	41,206
		Nine months ended			Nine months ended
	(in thousands)	September 30, 2014			September 30, 2013
	Balance at beginning of period	$	18,289		$	89,019
	Realized gains	8,581			41,952
	Unrealized losses relating to instruments held at the reporting date*	(3,734		)	(48,835		)
	Settlements during period	(8,250		)	(40,930		)
	Balance at end of period	$	14,886		$	41,206
	*Includes $12.2 million and $9.6 million in mark-to-market gains for the three months and nine months ended September 30, 2014, respectively. Includes $0.8 million and $4.7 million in mark-to-market gains for the three months and nine months ended September 30, 2013, respectively.
	The table below sets forth quantitative information about Energen’s Level 3 fair value measurements of derivative commodity instruments as follows:
	(in thousands, except price data)	Fair Value as of September 30, 2014			Valuation Technique*	Unobservable Input*	Range
	Oil Basis - WTS/WTI
	2014	$	1,115		Discounted Cash Flow	Forward Basis	($6.62) Bbl
	2015	(181		)	Discounted Cash Flow	Forward Basis	($4.20 - $4.24) Bbl
	Oil Basis - WTI/WTI
	2014	$	2,736		Discounted Cash Flow	Forward Basis	($7.07 - $7.18) Bbl
	2015	(1,979		)	Discounted Cash Flow	Forward Basis	($4.60 - $4.97) Bbl
	Natural Gas Liquids
	2014	$	1,600		Discounted Cash Flow	Forward Price	$0.67 - $0.90 Gal
	Natural Gas Basis - San Juan
	2014	$	4,946		Discounted Cash Flow	Forward Basis	($0.05 - $0.12) Mcf
	2015	$	5,097		Discounted Cash Flow	Forward Basis	($0.09 - $0.10) Mcf
	Natural Gas Basis - Permian
2014	$	(372	)	Discounted Cash Flow	Forward Basis	($0.09 - $0.10) Mcf
2015	$	1,924		Discounted Cash Flow	Forward Basis	($0.13) Mcf
*Discounted cash flow represents an income approach in calculating fair value including the referenced unobservable input and a discount reflecting credit quality of the counterparty.
Financial Instruments not Carried at Fair Value
The stated value of cash and cash equivalents, short-term investments, accounts receivable (net of allowance), and short-term debt approximates fair value due to the short maturity of the instruments. The fair value of Energen’s long-term debt, including the current portion, was approximately $637.3 million and $1,161.9 million and had a carrying value of $632.9 million and $1,154.0 million at September 30, 2014 and December 31, 2013, respectively. The fair values are based on market prices of similar debt issues having the same remaining maturities, redemption terms and credit rating. Short-term debt is classified as Level 1 fair value and long-term debt is classified as Level 2 fair value.

LongTerm_Debt_and_Notes_Payabl

Long-Term Debt and Notes Payable	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Long-Term Debt and Notes Payable	'
	LONG-TERM DEBT AND NOTES PAYABLE
	Long-term debt consisted of the following:
	(in thousands)	September 30, 2014			December 31, 2013
	Credit facility	$	78,900		$	—
	7.40% Medium-term Notes, Series A, due July 24, 2017	2,000			2,000
	7.36% Medium-term Notes, Series A, due July 24, 2017	15,000			15,000
	7.23% Medium-term Notes, Series A, due July 28, 2017	2,000			2,000
	7.32% Medium-term Notes, Series A, due July 28, 2022	20,000			20,000
	7.60% Medium-term Notes, Series A, due July 26, 2027	5,000			5,000
	7.35% Medium-term Notes, Series A, due July 28, 2027	10,000			10,000
	7.125% Medium-term Notes, Series B, due February 15, 2028	100,000			100,000
	4.625% Notes, due September 1, 2021	400,000			400,000
	Senior Term Loans, (floating rate interest LIBOR plus 1.625%)	—			600,000
		632,900			1,154,000
	Less amounts due within one year	—			60,000
	Less unamortized debt discount	442			459
	Total Energen	$	632,458		$	1,093,541
	The aggregate maturities of Energen’s long-term debt outstanding at September 30, 2014 are as follows:
	(in thousands)
	Remaining 2014	2015	2016	2017	2018	2019 and thereafter
	—	—	—	$19,000	—	$613,900
	In December 2013, Energen issued $600 million in Senior Term Loans (Senior Term Loans) with a floating interest rate due March 31, 2014 through December 17, 2017. In conjunction with the sale of Alagasco, the Senior Term Loans were repaid in September 2014.
	The debt agreements of Energen contain financial and nonfinancial covenants including routine matters such as timely payment of principal and interest, maintenance of corporate existence and restrictions on liens. Although none of the agreements have events of default based on credit ratings, the interest rates applicable to the syndicated credit facility discussed below may adjust based on credit rating changes during certain periods.
	Under Energen’s Indenture dated September 1, 1996 with The Bank of New York as Trustee, a cross default provision provides that any debt default of more than $10 million by Energen or Energen Resources will constitute an event of default by Energen. The Indenture does not include a restriction on the payment of dividends.
	Credit Facility: On September 2, 2014, Energen entered into a $1.5 billion five-year syndicated secured credit facility with domestic and foreign lenders. The credit facility has an initial borrowing base of $2.1 billion. This credit facility refinances and replaces the $1.25 billion five-year syndicated unsecured credit facility entered into on October 30, 2012. Energen’s obligations under the $1.5 billion syndicated credit facility are unconditionally guaranteed by Energen Resources. The current credit facility qualifies for classification as long-term debt on the consolidated balance sheets. The financial covenants of the credit facility require Energen to maintain a ratio of total debt to consolidated income before interest expense, income taxes, depreciation, depletion, amortization, exploration expense and other non-cash income and expenses (EBITDAX) less than or equal to 4.0 to 1.0, to maintain a ratio of consolidated current assets (adjusted to include amounts available for borrowings and exclude non-cash derivative instruments) to consolidated current liabilities (adjusted to exclude maturities under the credit facility and non-cash derivative instruments) greater than or equal to 1.0 to 1.0 and, during certain periods, to maintain a ratio of the net present value of proved reserves of our oil and natural gas properties to consolidated total debt greater than or equal to 1.50 to 1.0. We are also bound by covenants which limit our ability to incur additional indebtedness, make certain distributions or alter our corporate structure. Energen may not pay dividends during an event of default, if the payment would result in an event of default or if availability is less than 10 percent of the loan limit under the credit facility. Our credit facility also limits our ability to enter into commodity hedges based on projected production volumes.
	Under the credit facility, a cross default provision provides that any debt default of more than $75 million by Energen or Energen Resources will constitute an event of default by Energen.
	Upon an uncured event of default under the credit facility, all amounts owing under the credit facility, if any, depending on the nature of the event of default will automatically, or may upon notice by the administrative agent or the requisite lenders thereunder, become immediately due and payable and the lenders may terminate their commitments under the defaulted facility. Energen was in compliance with the terms of its credit facility as of September 30, 2014.
	The following is a summary of information relating to Energen’s credit facilities:
	(in thousands)	September 30, 2014			December 31, 2013
	Notes payable to banks	$	78,900		$	489,000
	Available for borrowings	1,421,100			761,000
	Total	$	1,500,000		$	1,250,000
	Maximum amount outstanding at any month-end	$	750,000		$	901,000
	Average daily amount outstanding	$	559,878		$	804,895
	Weighted average interest rates based on:
	Average daily amount outstanding	1.43		%	1.38		%
	Amount outstanding at period-end	1.66		%	1.32		%
	Energen’s interest expense was $11.5 million and $27.4 million for the three months and nine months ended September 30, 2014, respectively. Interest expense for Energen was $10.1 million and $30.2 million for the three months and nine months ended September 30, 2013, respectively. Energen had no capitalized interest for the three months ended September 30, 2014. For the nine months ended September 30, 2014, Energen’s total interest expense included capitalized interest of $37,000. Energen had no capitalized interest expense for the three months ended September 30, 2013. Energen’s total interest expense for the nine months ended September 30, 2013 included capitalized interest expense of $0.2 million. At September 30, 2014, Energen paid commitment fees on the unused portion of the available credit facilities at a current annual rate of 30 basis points. See Note 1, Organization and Basis of Presentation, for further information regarding interest on debt required to be extinguished, associated with the sale of Alagasco, which was classified to discontinued operations.

Reconciliation_of_Earnings_Per

Reconciliation of Earnings Per Share (EPS)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Reconciliation of Earnings Per Share (EPS)	'
	RECONCILIATION OF EARNINGS PER SHARE (EPS)
		Three months ended							Three months ended
	(in thousands, except per share amounts)	September 30, 2014							September 30, 2013
		Net				Per Share			Net				Per Share
		Income			Shares	Amount			Income			Shares	Amount
	Basic EPS	$	457,251		73,093	$	6.26		$	(19,298	)	72,346	$	(0.27	)
	Effect of dilutive securities
	Stock options				231							—
	Non-vested restricted stock				68							—
	Performance share awards				115							—
	Diluted EPS	$	457,251		73,507	$	6.22		$	(19,298	)	72,346	$	(0.27	)
	In periods of loss, shares that otherwise would have been included in diluted average common shares outstanding are excluded. The Company had 242,560 of excluded shares for the three months ended September 30, 2013.
		Nine months ended							Nine months ended
	(in thousands, except per share amounts)	September 30, 2014							September 30, 2013
		Net				Per Share			Net				Per Share
		Income			Shares	Amount			Income			Shares	Amount
	Basic EPS	$	502,614		72,861	$	6.9		$	120,461		72,220	$	1.67
	Effect of dilutive securities
	Stock options				219							41
	Non-vested restricted stock				67							10
	Performance share awards				91							1
	Diluted EPS	$	502,614		73,238	$	6.86		$	120,461		72,272	$	1.67
	Energen had the following shares that were excluded from the computation of diluted EPS, as inclusion would be anti-dilutive:
		Three months ended				Nine months ended
		September 30,				September 30,
	(in thousands)	2014		2013		2014		2013
	Stock options	6		—		6		875
	Performance share awards	2		—		4		79

Stock_Compensation

Stock Compensation	9 Months Ended
	Sep. 30, 2014
Share-based Compensation [Abstract]	'
Stock Compensation	'
	STOCK COMPENSATION
	Stock Incentive Plan
	Stock Options: The Stock Incentive Plan provides for the grant of incentive stock options and non-qualified stock options to officers and key employees. Options granted under the Stock Incentive Plan provide for the purchase of Energen common stock at not less than the fair market value on the date the option was granted. The sale or transfer of the shares is limited during certain periods. All outstanding options vest within three years from date of grant and expire 10 years from the grant date. Energen granted 107,868 non-qualified option shares during the first quarter of 2014 with a grant-date fair value of $27.57. During the second quarter of 2014, Energen granted 2,439 non-qualified option shares with a grant-date fair value of $32.22.
	Restricted Stock: Additionally, the Stock Incentive Plan provides for the grant of restricted stock units. In January 2014, Energen awarded 41,664 restricted stock units with a grant-date fair value of $70.68. Energen granted 928 restricted stock units during the second quarter of 2014 with a grant-date fair value of $79.15. These awards have a three year vesting period. Energen also granted 6,312 restricted stock units during the second quarter of 2014 with a grant-date fair value of $78.99 and a two year graded vesting period. These awards were valued based on the quoted market price of Energen’s common stock at the date of grant.
	Performance Share Awards: The Stock Incentive Plan also provides for the grant of performance share awards, with each unit equal to the market value of one share of common stock, to eligible employees based on predetermined Company performance criteria at the end of an award period. The Stock Incentive Plan provides that payment of earned performance share awards be made in the form of Energen common stock. Performance share awards are valued using the Monte Carlo model which uses historical volatility and other variables to estimate the probability of satisfying the market condition of the award. Energen granted 287 performance share awards during the first quarter of 2014 with a two year vesting period and a grant-date fair value of $118.99. Energen also granted 63,842 performance share awards during the first quarter of 2014 with a three year vesting period and a grant-date fair value of $93.13. During the second quarter of 2014, Energen granted 650 performance share awards with a two year vesting period and a grant-date fair value of $137.11. Energen also granted 1,467 performance share awards during the second quarter of 2014 with a three year vesting period and a grant-date fair value of $109.02.
	Stock Appreciation Rights Plan
	The Stock Appreciation Rights Plan provides for the payment of cash incentives measured by the long-term appreciation of Energen common stock. These awards are liability awards which settle in cash and are remeasured each reporting period until settlement and have a three year vesting period. Energen granted 62,749 awards during the first quarter of 2014. These awards had a fair value of $28.71 as of September 30, 2014.
	Petrotech Incentive Plan
	The Petrotech Incentive Plan provides for the grant of stock equivalent units. These awards are liability awards which settle in cash and are remeasured each reporting period until settlement. During the first quarter of 2014, Energen awarded 28,840 Petrotech units with a fair value of $72.06 as of September 30, 2014, none of which included a market condition. Also awarded were 36,920 Petrotech units which included a market condition and had a fair value of $94.38 as of September 30, 2014. These awards have a three year vesting period. During the third quarter of 2014, Energen Resources awarded 9,728 Petrotech units with a three-year vesting period and a fair value of $72.06 as of September 30, 2014, and 596 Petrotech units with a twenty-month vesting period and a fair value of $72.14 as of September 30, 2014, none of which included a market condition.
	Stock Repurchase Program
	During the three months and nine months ended September 30, 2014, Energen had non-cash purchases of approximately $36,000 and $0.4 million, respectively, of Energen common stock in conjunction with tax withholdings on our non-qualified deferred compensation plan and other stock compensation. Energen utilized internally generated cash flows in payment of the related tax withholdings.

Employee_Benefit_Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'
Employee Benefit Plans	'
	EMPLOYEE BENEFIT PLANS
	In October 2014, Energen’s Board of Directors elected to freeze and terminate its qualified defined benefit pension plan. A plan amendment adopted in October 2014 closes the plan to new entrants, effective November 1, 2014, and freezes benefit accruals after December 31, 2014. Energen intends to terminate the plan on January 31, 2015. We anticipate distributing benefits under the plan in late 2015 or early 2016 pending receipt of a determination letter from the Internal Revenue Service and completion of certain administrative actions.
	The Company’s non-qualified supplemental retirement plans will also be amended to terminate effective December 31, 2014. Distributions under the plans are subject to certain payment restrictions under the Internal Revenue Code and Treasury regulations and payments to plan participants will be made in each of the first quarters of 2015 and 2016. In connection with the termination of these plans, the Company has also reclassified approximately $17.1 million as of September 30, 2014 of its investment in a Rabbi Trust from other long term assets to prepayments and other assets in the accompanying balance sheets to reflect its intent to utilize these assets to fund the estimated payments in the first quarter of 2015.
	In October 2014, Energen’s Board of Directors amended and restated the Employee Saving Plan to make certain benefit design changes effective January 1, 2015. The benefit design changes are expected to include an increase in the percentage of Company match and other contributions.
	Effective April 30, 2014, Energen Corporation separated one of its defined benefit non-contributory pension plans into an Energen and an Alagasco plan reflecting the separation of assets and obligations in accordance with ERISA provisions. Energen remeasured our plans using current assumptions.
	The components of net periodic benefit cost for Energen’s defined benefit non-contributory pension plan and certain nonqualified supplemental pension plans were as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	1,902		$	1,326		$	5,157		$	3,980
	Interest cost	1,157			1,093			3,974			3,269
	Expected long-term return on assets	(1,157		)	(1,321		)	(4,067		)	(3,966		)
	Actuarial loss	1,296			1,760			4,115			5,417
	Prior service cost amortization	63			62			177			185
	Settlement charge	370			18			4,043			161
	Net periodic expense	$	3,631		$	2,938		$	13,399		$	9,046
	Energen is required to make approximately $7.7 million in contributions for 2014 to the qualified pension plans. This estimate includes required contributions for the Alagasco pension plans through August 31, 2014. In January 2014, we made a $3.0 million contribution and have utilized funding credits, as established under Internal Revenue Code Section 430(f), to meet the remaining required funding. We also made an additional discretionary contribution of $10 million to the Energen qualified pension plan in October 2014. We do not anticipate that the funded status of the qualified pension plans will fall below statutory thresholds requiring accelerated funding or constraints on benefit levels or plan administration. We may also make additional discretionary contributions to the qualified pension plan depending on the amount and timing of employee retirements and market conditions. For the three months and nine months ended September 30, 2014, Energen made benefit payments aggregating $74,000 and $1.0 million, respectively, to retirees from the non-qualified supplemental retirement plans and expects to make additional benefit payments of approximately $5.2 million through the remainder of 2014. In the third quarter of 2014, Energen incurred a settlement charge of $26,000 for the payment of lump sums from the non-qualified supplemental retirement plans. Also in the third quarter of 2014, Energen incurred settlement charges of $0.3 million for the payment of lump sums from the qualified defined benefit pension plan. In the second quarter of 2014, Energen incurred settlement charges of $0.4 million for the payment of lump sums from the qualified defined benefit pension plans. In the first quarter of 2014, Energen incurred settlement charges of $6.9 million for the payment of lump sums from the qualified defined benefit pension plans of which $3.7 million is included in discontinued operations. Also in the first quarter of 2014, Energen incurred a settlement charge of $0.4 million for the payment of lump sums from the non-qualified supplemental retirement plans. In the third quarter of 2013, Energen incurred a settlement charge of $18,000 for the payment of lump sums from the non-qualified supplemental retirement plans. In the first quarter of 2013, Energen incurred a settlement charge of $0.1 million for the payment of lump sums from the non-qualified supplemental retirement plans.
	Also effective April 30, 2014, Energen Corporation separated its postretirement health care and life insurance benefit plans into separate plans established for Energen and Alagasco employees in accordance with ERISA provisions. Energen remeasured our plan using current assumptions.
	The components of net periodic postretirement benefit expense for Energen’s postretirement benefit plan were as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	87		$	111		$	206		$	334
	Interest cost	137			175			587			526
	Expected long-term return on assets	(246		)	(212		)	(1,016		)	(638		)
	Actuarial gain	(151		)	—			(572		)	—
	Transition amortization	9			63			39			189
	Net periodic (income) expense	$	(164	)	$	137		$	(756	)	$	411
	There are no required contributions to the postretirement benefit plan during 2014.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	COMMITMENTS AND CONTINGENCIES
	Commitments and Agreements: Under various agreements for third-party gathering, treatment, transportation or other services, Energen is committed to deliver minimum production volumes or to pay certain costs in the event the minimum quantities are not delivered. These delivery commitments are approximately 6 million barrels of oil equivalent (MMBOE) through September 2017.
	Legal Matters: Energen and its affiliates are, from time to time, parties to various pending or threatened legal proceedings and we have accrued a provision for our estimated liability. Certain of these lawsuits include claims for punitive damages in addition to other specified relief. We recognize a liability for contingencies when information available indicates both a loss is probable and the amount of the loss can be reasonably estimated. Based upon information presently available, and in light of available legal and other defenses, contingent liabilities arising from threatened and pending litigation are not considered material in relation to the respective financial positions of Energen and its affiliates. It should be noted, however, that there is uncertainty in the valuation of pending claims and prediction of litigation results.
	Energen Resources previously disclosed an adverse judgment relating to the ownership of the Company operated Cadenhead 25-1 Well (the Cadenhead Well) in Ward County, Texas. Upon a Motion to Reconsider, the adverse judgment was vacated by the District Court in Ward County, Texas and a Summary Judgment Order dated July 30, 2013 was entered confirming Energen Resources’ superior title to the Cadenhead Well and its associated oil and gas leases. The Summary Judgment Order has been affirmed by the Court of Appeals for the Eighth District of Texas.
	Environmental Matters: Various environmental laws and regulations apply to the operations of Energen and Energen Resources. Historically, the cost of environmental compliance has not materially affected our financial position, results of operations or cash flows. New regulations, enforcement policies, claims for damages or other events could result in significant unanticipated costs.
	Under oversight of the Site Remediation Section of the Railroad Commission of Texas, Energen Resources is currently in the process of cleanup and remediation of oil and gas wastes in nine reserve pits in Mitchell County, Texas. We estimate that the cleanup, remediation and related costs will approximate $4.1 million of which $3.4 million has been incurred.
	During January 2014, Energen Resources responded to a General Notice and Information Request from the Environmental Protection Agency regarding the Reef Environmental Site in Sylacauga, Talladega County, Alabama. The letter identifies Energen Resources as a potentially responsible party under The Comprehensive Environmental Response, Compensation, and Liability Act for the cleanup of the Site. In 2008, Energen hired a third party to transport approximately 3,000 gallons of non-hazardous wastewater to Reef Environmental for wastewater treatment. Reef Environmental ceased operating its wastewater treatment system in 2010. Due to its one time use of Reef Environmental for a small volume of non-hazardous wastewater, Energen Resources has not accrued a liability for cleanup of the Site.
	New Mexico Audits: In 2011, Energen Resources received an Order to Perform Restructured Accounting and Pay Additional Royalties (the Order), following an audit performed by the Taxation and Revenue Department (the Department) of the State of New Mexico on behalf of the Office of Natural Resources Revenue (ONRR), of federal oil and gas leases in New Mexico. The audit covered periods from January 2004 through December 2008 and included a review of the computation and payment of royalties due on minerals removed from specified U.S. federal leases. The Order addressed ONRR’s efforts to change accounting and reporting practices, and to unbundle fees charged by third parties that gather, compress and transport natural gas production. ONRR now maintains that all or some of such fees are not deductible.
	Energen Resources appealed the Order in 2011 and in July 2012, on a motion from ONRR, the Order was remanded. In August 2014, ONRR issued its Revised Order that is now under appeal. In the Revised Order, ONRR has ordered that Energen pay additional royalties on production from certain federal leases in the amount of $129,700. Energen estimates that application of the Revised Order to all of the Company’s federal leases would result in ONRR claims up to approximately $23 million, plus interest and penalties from 2004 forward. ONRR began implementing its unbundling initiative in 2010, but seeks to implement its revisions retroactively, despite the fact that they conflict with previous audits, allowances and industry practice. Energen continues to vigorously contest the Revised Order and the findings. Management is unable, at this time, to determine a range of reasonably possible losses, and no amount has been accrued as of September 30, 2014.

Exploratory_Costs

Exploratory Costs	9 Months Ended
	Sep. 30, 2014
Extractive Industries [Abstract]	'
Exploratory Costs	'
	EXPLORATORY COSTS
	Energen capitalizes exploratory drilling costs until a determination is made that the well or project has either found proved reserves or is impaired. After an exploratory well has been drilled and found oil and natural gas reserves, a determination may be pending as to whether the oil and natural gas quantities can be classified as proved. In those circumstances, Energen continues to capitalize the drilling costs pending the determination of proved status if (i) the well has found a sufficient quantity of reserves to justify its completion as a producing well and (ii) Energen is making sufficient progress assessing the reserves and the economic and operating viability of the project. Capitalized exploratory drilling costs are presented in unproved properties in the balance sheets. If the exploratory well is determined to be impaired, the impaired costs are charged to exploration expense. Other exploration costs, including geological and geophysical costs, are expensed as incurred.
	The following table sets forth capitalized exploratory well costs and includes additions pending determination of proved reserves, reclassifications to proved reserves and costs charged to expense:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Capitalized exploratory well costs at beginning of period	$	166,458		$	72,172		$	57,600		$	79,791
	Additions pending determination of proved reserves	258,724			99,428			623,913			319,008
	Reclassifications due to determination of proved reserves	(258,123		)	(112,821		)	(513,263		)	(340,020		)
	Exploratory well costs charged to expense	(1,217		)	—			(2,408		)	—
	Capitalized exploratory well costs at end of period	$	165,842		$	58,779		$	165,842		$	58,779
	The following table sets forth capitalized exploratory wells costs and includes amounts capitalized for a period greater than one year:
	(in thousands)	September 30, 2014			December 31, 2013
	Exploratory wells in progress	$	29,059		$	14,794
	Capitalized exploratory well costs capitalized for a period of one year or less	136,783			42,481
	Capitalized exploratory well costs for a period greater than one year	—			1,206
	Total capitalized exploratory well costs	$	165,842		$	58,481
	At September 30, 2014, Energen had 56 gross exploratory wells either drilling or waiting on results from completion and testing. These wells are located primarily in the Permian Basin.

Asset_Retirement_Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	ASSET RETIREMENT OBLIGATIONS
	Energen’s asset retirement obligations (ARO) primarily relate to the future plugging, abandonment and reclamation of wells and facilities. We recognize a liability for the fair value of the ARO in the periods incurred. The ARO fair value liability is determined by calculating the present value of the estimated future cash outflows we expect to incur to plug, abandon and reclaim our producing properties at the end of their productive lives, and is recognized on a discounted basis incorporating an estimate of performance risk specific to Energen. Subsequent to initial measurement, liabilities are accreted to their present value and capitalized costs are depreciated over the estimated useful lives of the related assets. Upon settlement of the liability, Energen may recognize a gain or loss for differences between estimated and actual settlement costs.
	The following table reflects the components of the change in Energen’s ARO balance for the nine months ended September 30, 2014:
	(in thousands)
	Balance as of December 31, 2013	$	108,533
	Liabilities incurred	2,265
	Liabilities settled	(1,017		)
	Accretion expense	5,650
	Balance as of September 30, 2014	$	115,431

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)
	The following table provides changes in the components of accumulated other comprehensive income (loss), net of the related income tax effects.
	(in thousands)	Cash Flow Hedges			Pension and Postretirement Plans			Total
	Balance as of December 31, 2013	$	12,178		$	(32,245	)	$	(20,067	)
	Other comprehensive loss before reclassifications	(258		)	(1,784		)	(2,042		)
	Amounts reclassified from accumulated other comprehensive income (loss)	(8,302		)	7,716			(586		)
	Change in accumulated other comprehensive income (loss)	(8,560		)	5,932			(2,628		)
	Balance as of September 30, 2014	$	3,618		$	(26,313	)	$	(22,695	)
	The following table provides details of the reclassifications out of accumulated other comprehensive income (loss).
		Three months ended			Three months ended
		30-Sep-14			30-Sep-13
	(in thousands)	Amounts Reclassified						Line Item Where Presented
	Gains (losses) on cash flow hedges:
	Commodity contracts	$	5,992		$	8,433		Gain (loss) on derivative instruments, net
	Interest rate swap	(247		)	(446		)	Interest expense
	Total cash flow hedges	5,745			7,987
	Income tax expense	(2,191		)	(3,048		)
	Net of tax	3,554			4,939
	Pension and postretirement plans:
	Transition obligation	2			(74		)	General and administrative
	Prior service cost	(74		)	(78		)	General and administrative
	Actuarial losses*	(1,060		)	(2,036		)	General and administrative
	Actuarial losses on settlement charges	(370		)	—			General and administrative
	Actuarial losses on settlement charges*	—			(46		)	Assets held for sale with prior period comparable
	Total pension and postretirement plans	(1,502		)	(2,234		)
	Income tax expense	525			783
	Net of tax	(977		)	(1,451		)
	Total reclassifications for the period	$	2,577		$	3,488
		Nine months ended			Nine months ended
		30-Sep-14			30-Sep-13
	(in thousands)	Amounts Reclassified						Line Item Where Presented
	Gains (losses) on cash flow hedges:
	Commodity contracts	$	15,781		$	30,226		Gain (loss) on derivative instruments, net
	Interest rate swap	(2,280		)	(1,282		)	Interest expense
	Total cash flow hedges	13,501			28,944
	Income tax expense	(5,199		)	(11,037		)
	Net of tax	8,302			17,907
	Pension and postretirement plans:
	Transition obligation	(17		)	(220		)	General and administrative
	Prior service cost	(222		)	(235		)	General and administrative
	Actuarial losses*	(3,640		)	(6,387		)	General and administrative
	Actuarial losses on settlement charges	(7,992		)	—			General and administrative
	Actuarial losses on settlement charges*	—			(421		)	Assets held for sale with prior period comparable
	Total pension and postretirement plans	(11,871		)	(7,263		)
	Income tax expense	4,155			2,542
	Net of tax	(7,716		)	(4,721		)
	Total reclassifications for the period	$	586		$	13,186
	* In the first quarter of 2013, Energen incurred a settlement charge of $0.5 million for the payment of lump sums from the nonqualified supplemental retirement plans, of which $0.1 million was recognized in actuarial losses above and $0.4 million was recognized as a regulatory asset at Alagasco and reported in actuarial losses on settlement charges above. In the third quarter of 2013, Energen incurred a settlement charge of $64,000 for the payment of lump sums from the nonqualified supplemental retirement plans, of which $18,000 is recognized in actuarial losses above and $46,000 was recognized as a regulatory asset at Alagasco and reported in actuarial losses on settlement charges above.

Discontinued_Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Discontinued Operations	'
	DISCONTINUED OPERATIONS
	On September 2, 2014, Energen completed the transaction to sell Alagasco to Laclede for $1.6 billion, less the assumption of $267 million in debt. The net pre-tax proceeds to Energen totaled approximately $1.32 billion, subject to closing adjustments. This sale has an effective date of August 31, 2014. Energen used cash proceeds from the sale to reduce long-term and short-term indebtedness. During the second quarter of 2014, Energen classified Alagasco as held for sale with prior period comparable and reflected the associated operating results in discontinued operations. Energen’s results of operations for the three months and nine months ended September 30, 2014 and 2013 and our financial position as of September 30, 2014 and December 31, 2013 presented in our unaudited consolidated financial statements and these notes reflect Alagasco as discontinued operations.
	In March 2014, Energen completed the sale of its North Louisiana/East Texas natural gas and oil properties for $30.3 million (subject to closing adjustments). The sale had an effective date of December 1, 2013, and the proceeds from the sale were used to repay short-term obligations. During the third quarter of 2013, Energen classified these natural gas and oil properties as held for sale and reflected the associated operating results in discontinued operations. Energen recognized a non-cash impairment writedown on these properties in the first quarter of 2014 of $1.7 million pre-tax to adjust the carrying amount of these properties to their fair value based on an estimate of the selling price of the properties. This non-cash impairment writedown is reflected in loss on disposal of discontinued operations in the nine months ended September 30, 2014. Energen also recognized non-cash impairment writedowns on these properties in the third and fourth quarters of 2013 of $24.6 million pre-tax and $5.2 million pre-tax, respectively. Significant assumptions in valuing the proved reserves included the reserve quantities, anticipated operating costs, anticipated production taxes, future expected natural gas prices and basis differentials, anticipated production declines, and a discount rate of 10 percent commensurate with the risk of the underlying cash flow estimates. The impairment writedowns are classified as Level 3 fair value. At December 31, 2013, proved reserves associated with Energen’s North Louisiana/East Texas properties totaled 23 Bcf of natural gas and 91 MBbl of oil.
	In October 2013, Energen completed the sale of its Black Warrior Basin coalbed methane properties in Alabama for $160 million (subject to closing adjustments). Energen recorded a pre-tax gain on the sale of approximately $35 million in the fourth quarter of 2013 which was reflected in gain on disposal of discontinued operations in the year ended December 31, 2013. The sale had an effective date of July 1, 2013, and the proceeds from the sale were used to repay short-term obligations. The property was classified as held for sale and reflected in discontinued operations during the third quarter of 2013. At December 31, 2012, proved reserves associated with Energen’s Black Warrior Basin properties totaled 97 Bcf of natural gas.
	The following table details held for sale properties by major classes of assets and liabilities:
	(in thousands)	31-Dec-13
		Alabama Gas Corporation			Black Warrior Basin			North Louisiana/East Texas			Total
	Cash	$	3,032		$	—		$	—		$	3,032
	Accounts receivable*	103,748			2,829			1,272			107,849
	Inventories	41,200			—			68			41,268
	Oil and gas properties	—			—			348,379			348,379
	Less accumulated depreciation, depletion and amortization	—						(301,609		)	(301,609		)
	Utility plant	1,491,433			—			—			1,491,433
	Less accumulated depreciation	(605,924		)	—			—			(605,924		)
	Other property, net	41			—			165			206
	Other current assets*	29,458			—			—			29,458
	Other long-term assets	128,780			—			—			128,780
	Total assets held for sale	1,191,768			2,829			48,275			1,242,872
	Accounts payable	(48,653		)	(1,732		)	(11		)	(50,396		)
	Royalty payable	—			(550		)	(869		)	(1,419		)
	Accrued taxes	(28,027		)	—			—			(28,027		)
	Notes payable to banks	(50,000		)	—			—			(50,000		)
	Other current liabilities*	(105,013		)	(379		)	(21		)	(105,413		)
	Other long-term liabilities	(331,409		)	—			(14,983		)	(346,392		)
	Long-term debt	(249,923		)	—			—			(249,923		)
	Total liabilities held for sale	(813,025		)	(2,661		)	(15,884		)	(831,570		)
	Total net assets held for sale	$	378,743		$	168		$	32,391		$	411,302
	*At December 31, 2013, Alagasco’s accounts receivable included a consolidating adjustment of $4.7 million to adjust for affiliated companies receivables. Certain other current assets and other current liabilities at Alagasco of $1.6 million and $0.5 million, respectively, were reclassified to continuing operations at Energen.
	We recognized interest on debt required to be extinguished in connection with the sale of Alagasco as discontinued operations. On September 2, 2014, Energen entered into a $1.5 billion five-year syndicated secured credit facility with domestic and foreign lenders. This credit facility refinances and replaces the $1.25 billion five-year syndicated unsecured credit facilities entered into on October 30, 2012. The interest associated with the October 2012 five-year syndicated unsecured credit facilities was classified as discontinued operations. See Note 1, Organization and Basis of Presentation, for further information regarding adjustments associated with the sale of Alagasco.
	Gains and losses on the sale of certain oil and natural gas properties as well as any impairments of properties held for sale are reported as discontinued operations, with income or loss from operations of the associated assets reported as income or loss from discontinued operations. The results of operations for certain held for sale assets were reclassified and reported as discontinued operations for all prior periods presented. Energen may, in the ordinary course of business, be involved in the sale of developed or undeveloped properties. All assets held for sale are reported at the lower of the carrying amount or fair value.
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands, except per share data)	2014			2013			2014			2013
	Natural gas distribution revenues	$	39,874		$	48,368		$	397,648		$	390,567
	Oil and natural gas revenues	6			18,258			5,217			55,483
	Total revenues	$	39,880		$	66,626		$	402,865		$	446,050
	Pretax income (loss) from discontinued operations	$	(5,938	)	$	(14,677	)	$	48,581		$	64,098
	Income tax expense (benefit)	(2,453		)	(5,650		)	18,146			24,207
	Income (Loss) From Discontinued Operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891
	Gain (loss) on disposal of discontinued operations	$	726,410		$	(24,612	)	$	724,743		$	(24,612	)
	Income tax expense (benefit)	286,305			(8,934		)	285,688			(8,934		)
	Gain (Loss) on Disposal of Discontinued Operations	$	440,105		$	(15,678	)	$	439,055		$	(15,678	)
	Total Income (Loss) From Discontinued Operations	$	436,620		$	(24,705	)	$	469,490		$	24,213
	Diluted Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	5.99			(0.22		)	5.99			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.94		$	(0.34	)	$	6.41		$	0.34
	Basic Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	6.03			(0.22		)	6.03			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.98		$	(0.34	)	$	6.45		$	0.34

Acquisition_and_Disposition_of

Acquisition and Disposition of Properties	9 Months Ended
	Sep. 30, 2014
Business Acquisitions and Dispositions [Abstract]	'
Acquisition and Disposition of Properties	'
	ACQUISITION AND DISPOSITION OF PROPERTIES
	During the third quarter of 2014, Energen recognized a non-cash impairment writedown on certain properties in the Permian Basin of $31.2 million pre-tax to adjust the carrying amount of these properties to their fair value based on expected future discounted cash flows in anticipation of being designated as held for sale. This non-cash impairment writedown is reflected in asset impairment on the consolidated income statement.
	During the third quarter of 2014, a non-cash impairment writedown of $147.9 million pre-tax was recognized by Energen on certain gas properties in the San Juan Basin to adjust the carrying amount of these properties to their fair value based on expected future discounted cash flows in anticipation of being designated as held for sale. This non-cash impairment writedown is reflected in asset impairment on the consolidated income statement. At December 31, 2013, proved reserves associated with Energen’s San Juan Basin properties totaled 73,070 MBOE.
	In October 2014, Energen purchased approximately 15,000 net acres of unproved leasehold in the Mancos formation oil play in the San Juan Basin for $22.8 million.

Recently_Issued_Accounting_Sta

Recently Issued Accounting Standards	9 Months Ended
	Sep. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Recently Issued Accounting Standards	'
	RECENTLY ISSUED ACCOUNTING STANDARDS
	In April 2014, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. This update defines a discontinued operation as a disposal of a component or a group of components that is disposed of or is classified as held for sale and represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results. The amendment is effective for all annual periods beginning on or after December 15, 2014, and interim periods within those annual periods. Energen is currently evaluating the impact of the adoption of this ASU on its classification of future dispositions as discontinued operations.

Recently_Issued_Accounting_Sta1

Recently Issued Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
New Accounting Pronouncements, Policy	'
	RECENTLY ISSUED ACCOUNTING STANDARDS
	In April 2014, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. This update defines a discontinued operation as a disposal of a component or a group of components that is disposed of or is classified as held for sale and represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results. The amendment is effective for all annual periods beginning on or after December 15, 2014, and interim periods within those annual periods. Energen is currently evaluating the impact of the adoption of this ASU on its classification of future dispositions as discontinued operations.

Organization_and_Basis_of_Pres1

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Derivative Instruments, Gain (Loss)	'
	We further reclassified all commodity hedges from oil and natural gas operating revenues to gain (loss) on derivative instruments, net, as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Open non-cash mark-to-market gains (losses) on derivative instruments	$	147,287		$	(63,560	)	$	53,985		$	(48,459	)
	Closed gains (losses) on derivative instruments	448			(24,632		)	(44,487		)	(3,445		)
	Gain (loss) on derivative instruments, net	$	147,735		$	(88,192	)	$	9,498		$	(51,904	)
Schedule of Discontinued Operations	'
	The table below provides a detail of these items included in income (loss) from discontinued operations at September 30, 2014:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Alagasco net income (loss)	$	(1,767	)	$	(8,961	)	$	40,646		$	37,557
	Depreciation, depletion and amortization	(103		)	(150		)	(408		)	(443		)
	General and administrative	1,710			1,158			3,337			4,784
	Interest expense	(4,329		)	(3,676		)	(17,306		)	(9,786		)
	Other income	—			(409		)	(347		)	(882		)
	Income tax expense	1,029			1,145			5,567			2,392
	Alagasco income (loss) from discontinued operations	(3,460		)	(10,893		)	31,489			33,622
	Energen income (loss) from discontinued operations	(25		)	1,866			(1,054		)	6,269
	Income (loss) from discontinued operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891
	The following table details held for sale properties by major classes of assets and liabilities:
	(in thousands)	31-Dec-13
		Alabama Gas Corporation			Black Warrior Basin			North Louisiana/East Texas			Total
	Cash	$	3,032		$	—		$	—		$	3,032
	Accounts receivable*	103,748			2,829			1,272			107,849
	Inventories	41,200			—			68			41,268
	Oil and gas properties	—			—			348,379			348,379
	Less accumulated depreciation, depletion and amortization	—						(301,609		)	(301,609		)
	Utility plant	1,491,433			—			—			1,491,433
	Less accumulated depreciation	(605,924		)	—			—			(605,924		)
	Other property, net	41			—			165			206
	Other current assets*	29,458			—			—			29,458
	Other long-term assets	128,780			—			—			128,780
	Total assets held for sale	1,191,768			2,829			48,275			1,242,872
	Accounts payable	(48,653		)	(1,732		)	(11		)	(50,396		)
	Royalty payable	—			(550		)	(869		)	(1,419		)
	Accrued taxes	(28,027		)	—			—			(28,027		)
	Notes payable to banks	(50,000		)	—			—			(50,000		)
	Other current liabilities*	(105,013		)	(379		)	(21		)	(105,413		)
	Other long-term liabilities	(331,409		)	—			(14,983		)	(346,392		)
	Long-term debt	(249,923		)	—			—			(249,923		)
	Total liabilities held for sale	(813,025		)	(2,661		)	(15,884		)	(831,570		)
	Total net assets held for sale	$	378,743		$	168		$	32,391		$	411,302
	*At December 31, 2013, Alagasco’s accounts receivable included a consolidating adjustment of $4.7 million to adjust for affiliated companies receivables. Certain other current assets and other current liabilities at Alagasco of $1.6 million and $0.5 million, respectively, were reclassified to continuing operations at Energen.
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands, except per share data)	2014			2013			2014			2013
	Natural gas distribution revenues	$	39,874		$	48,368		$	397,648		$	390,567
	Oil and natural gas revenues	6			18,258			5,217			55,483
	Total revenues	$	39,880		$	66,626		$	402,865		$	446,050
	Pretax income (loss) from discontinued operations	$	(5,938	)	$	(14,677	)	$	48,581		$	64,098
	Income tax expense (benefit)	(2,453		)	(5,650		)	18,146			24,207
	Income (Loss) From Discontinued Operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891
	Gain (loss) on disposal of discontinued operations	$	726,410		$	(24,612	)	$	724,743		$	(24,612	)
	Income tax expense (benefit)	286,305			(8,934		)	285,688			(8,934		)
	Gain (Loss) on Disposal of Discontinued Operations	$	440,105		$	(15,678	)	$	439,055		$	(15,678	)
	Total Income (Loss) From Discontinued Operations	$	436,620		$	(24,705	)	$	469,490		$	24,213
	Diluted Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	5.99			(0.22		)	5.99			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.94		$	(0.34	)	$	6.41		$	0.34
	Basic Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	6.03			(0.22		)	6.03			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.98		$	(0.34	)	$	6.45		$	0.34

Derivative_Commodity_Instrumen1

Derivative Commodity Instruments Derivative Commodity Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Schedule of Derivative Liabilities at Fair Value	'
	The following tables detail the offsetting of derivative assets and liabilities as well as the fair values of derivatives on the balance sheets:
	(in thousands)	30-Sep-14
											Gross Amounts Not Offset in the Balance Sheets
		Gross Amounts Recognized at Fair Value			Gross Amounts Offset in the Balance Sheets			Net Amount Presented in the Balance Sheets			Financial Instruments		Cash Collateral Received		Net Fair Value Presented in the Balance Sheets
	Derivatives not designated as hedging instruments
	Assets
	Derivative instruments	$	37,039		$	(6,844	)	$	30,195		$	—	$	—	$	30,195
	Noncurrent derivative instruments	6,581			(823		)	5,758			—		—		5,758
	Total derivative assets	43,620			(7,667		)	35,953			—		—		35,953
	Liabilities
	Derivative instruments	7,652			(6,844		)	808			—		—		808
	Noncurrent derivative instruments	1,463			(823		)	640			—		—		640
	Total derivative liabilities	9,115			(7,667		)	1,448			—		—		1,448
	Total derivatives	$	34,505		$	—		$	34,505		$	—	$	—	$	34,505
	(in thousands)	31-Dec-13
											Gross Amounts Not Offset in the Balance Sheets
		Gross Amounts Recognized at Fair Value			Gross Amounts Offset in the Balance Sheets			Net Amount Presented in the Balance Sheets			Financial Instruments		Cash Collateral Received		Net Fair Value Presented in the Balance Sheets
	Derivatives not designated as hedging instruments
	Assets
	Derivative instruments	$	36,223		$	(18,760	)	$	17,463		$	—	$	—	$	17,463
	Noncurrent derivative instruments	7,992			(2,553		)	5,439			—		—		5,439
	Total derivative assets	44,215			(21,313		)	22,902			—		—		22,902
	Liabilities
	Derivative instruments	49,062			(18,760		)	30,302			—		—		30,302
	Noncurrent derivative instruments	2,553			(2,553		)	—			—		—		—
	Total derivative liabilities	51,615			(21,313		)	30,302			—		—		30,302
	Total derivatives	$	(7,400	)	$	—		$	(7,400	)	$	—	$	—	$	(7,400	)
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location	'
	The following tables detail the effect of derivative commodity instruments in cash flow hedging relationships on the financial statements:
	(in thousands)	Location on Statements of Income	Three months			Three months
			ended			ended
			30-Sep-14			30-Sep-13
	Net gain recognized in other comprehensive income on derivatives (effective portion), net of tax of $18 and $42	—	$	29		$	69
	Gain reclassified from accumulated other comprehensive income into income (effective portion)	Gain (loss) on derivative instruments, net	$	5,992		$	8,455
	Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	Gain (loss) on derivative instruments, net	$	—		$	(22	)
	(in thousands)	Location on Statements of Income	Nine months			Nine months
			ended			ended
			30-Sep-14			30-Sep-13
	Net gain (loss) recognized in other comprehensive income on derivatives (effective portion), net of tax of $25 and ($6,669)	—	$	40		$	(10,882	)
	Gain reclassified from accumulated other comprehensive income into income (effective portion)	Gain (loss) on derivative instruments, net	$	15,781		$	29,391
	Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	Gain (loss) on derivative instruments, net	$	—		$	835
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	'
	The following tables detail the effect of open and closed derivative commodity instruments not designated as hedging instruments on the income statement:
	(in thousands)	Location on Statements of Income	Three months			Three months
			ended			ended
			30-Sep-14			30-Sep-13
	Gain (loss) recognized in income on derivatives	Gain (loss) on derivative instruments, net	$	141,743		$	(92,313	)
	(in thousands)	Location on Statements of Income	Nine months			Nine months
			ended			ended
			30-Sep-14			30-Sep-13
	Loss recognized in income on derivatives	Gain (loss) on derivative instruments, net	$	(6,283	)	$	(70,735	)
Schedule of Hedging Transactions	'
	As of September 30, 2014, Energen had entered into the following transactions for the remainder of 2014 and subsequent years:
	Production Period	Total Hedged Volumes		Average Contract	Description
				Price
	Oil
	2014	2,502	MBbl	$92.66 Bbl	NYMEX Swaps
	2015	8,280	MBbl	$89.30 Bbl	NYMEX Swaps
	Oil Basis Differential
	2014	300	MBbl	$(3.30) Bbl	WTS/WTI Basis Swaps*
	2014	600	MBbl	$(3.08) Bbl	WTI/WTI Basis Swaps**
	2015	2,160	MBbl	$(4.30) Bbl	WTS/WTI Basis Swaps*
	2015	6,120	MBbl	$(5.11) Bbl	WTI/WTI Basis Swaps**
	Natural Gas Liquids
	2014	18.5	MMgal	$0.93 Gal	Liquids Swaps
	Natural Gas
	2014	2.6	Bcf	$4.57 Mcf	NYMEX Swaps
	2014	7.6	Bcf	$4.62 Mcf	Basin Specific Swaps - San Juan
	2014	2.6	Bcf	$3.81 Mcf	Basin Specific Swaps - Permian
	2015	23	Bcf	$4.13 Mcf	Basin Specific Swaps - San Juan
	2015	6	Bcf	$4.20 Mcf	Basin Specific Swaps - Permian
	Natural Gas Basis Differential
	2014	1.5	Bcf	$(0.09) Mcf	San Juan Basis Swaps
	2014	0.6	Bcf	$(0.17) Mcf	Permian Basis Swaps
	*WTS - West Texas Sour/Midland, WTI - West Texas Intermediate/Cushing
	**WTI - West Texas Intermediate/Midland, WTI - West Texas Intermediate/Cushing

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Assets and Liabilities Measured at Fair Value on a Recurring Basis	'
	The following fair value hierarchy tables present information about Energen’s assets and liabilities measured at fair value on a recurring basis:
		September 30, 2014
	(in thousands)	Level 2			Level 3			Total
	Assets:
	Derivative instruments	$	16,355		$	13,840		$	30,195
	Noncurrent derivative instruments	4,763			995			5,758
	Total assets	21,118			14,835			35,953
	Liabilities:
	Derivative instruments	(1,499		)	691			(808		)
	Noncurrent derivative instruments	—			(640		)	(640		)
	Total liabilities	(1,499		)	51			(1,448		)
	Net derivative asset	$	19,619		$	14,886		$	34,505
		31-Dec-13
	(in thousands)	Level 2			Level 3			Total
	Assets:
	Derivative instruments	$	(1,658	)	$	19,121		$	17,463
	Noncurrent derivative instruments	4,383			1,056			5,439
	Total assets	2,725			20,177			22,902
	Liabilities:
	Derivative instruments	(28,414		)	(1,888		)	(30,302		)
	Total liabilities	(28,414		)	(1,888		)	(30,302		)
	Net derivative asset (liability)	$	(25,689	)	$	18,289		$	(7,400	)
Schedule of Changes in Fair Value of Derivative Instruments Classified as Level 3	'
	The tables below set forth a summary of changes in the fair value of Energen’s Level 3 derivative commodity instruments as follows:
		Three months ended			Three months ended
	(in thousands)	September 30, 2014			September 30, 2013
	Balance at beginning of period	$	5,207		$	51,131
	Realized gains	10,769			10,852
	Unrealized gains (losses) relating to instruments held at the reporting date*	9,348			(10,947		)
	Settlements during period	(10,438		)	(9,830		)
	Balance at end of period	$	14,886		$	41,206
		Nine months ended			Nine months ended
	(in thousands)	September 30, 2014			September 30, 2013
	Balance at beginning of period	$	18,289		$	89,019
	Realized gains	8,581			41,952
	Unrealized losses relating to instruments held at the reporting date*	(3,734		)	(48,835		)
	Settlements during period	(8,250		)	(40,930		)
	Balance at end of period	$	14,886		$	41,206
	*Includes $12.2 million and $9.6 million in mark-to-market gains for the three months and nine months ended September 30, 2014, respectively. Includes $0.8 million and $4.7 million in mark-to-market gains for the three months and nine months ended September 30, 2013, respectively.
Schedule of Fair Value Inputs, Derivatives, Quantitative Information	'
	The table below sets forth quantitative information about Energen’s Level 3 fair value measurements of derivative commodity instruments as follows:
	(in thousands, except price data)	Fair Value as of September 30, 2014			Valuation Technique*	Unobservable Input*	Range
	Oil Basis - WTS/WTI
	2014	$	1,115		Discounted Cash Flow	Forward Basis	($6.62) Bbl
	2015	(181		)	Discounted Cash Flow	Forward Basis	($4.20 - $4.24) Bbl
	Oil Basis - WTI/WTI
	2014	$	2,736		Discounted Cash Flow	Forward Basis	($7.07 - $7.18) Bbl
	2015	(1,979		)	Discounted Cash Flow	Forward Basis	($4.60 - $4.97) Bbl
	Natural Gas Liquids
	2014	$	1,600		Discounted Cash Flow	Forward Price	$0.67 - $0.90 Gal
	Natural Gas Basis - San Juan
	2014	$	4,946		Discounted Cash Flow	Forward Basis	($0.05 - $0.12) Mcf
	2015	$	5,097		Discounted Cash Flow	Forward Basis	($0.09 - $0.10) Mcf
	Natural Gas Basis - Permian
	2014	$	(372	)	Discounted Cash Flow	Forward Basis	($0.09 - $0.10) Mcf
	2015	$	1,924		Discounted Cash Flow	Forward Basis	($0.13) Mcf
	*Discounted cash flow represents an income approach in calculating fair value including the referenced unobservable input and a discount reflecting credit quality of the counterparty.

LongTerm_Debt_and_Notes_Payabl1

Long-Term Debt and Notes Payable (Tables)	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Long-term debt	'
	Long-term debt consisted of the following:
	(in thousands)	September 30, 2014			December 31, 2013
	Credit facility	$	78,900		$	—
	7.40% Medium-term Notes, Series A, due July 24, 2017	2,000			2,000
	7.36% Medium-term Notes, Series A, due July 24, 2017	15,000			15,000
	7.23% Medium-term Notes, Series A, due July 28, 2017	2,000			2,000
	7.32% Medium-term Notes, Series A, due July 28, 2022	20,000			20,000
	7.60% Medium-term Notes, Series A, due July 26, 2027	5,000			5,000
	7.35% Medium-term Notes, Series A, due July 28, 2027	10,000			10,000
	7.125% Medium-term Notes, Series B, due February 15, 2028	100,000			100,000
	4.625% Notes, due September 1, 2021	400,000			400,000
	Senior Term Loans, (floating rate interest LIBOR plus 1.625%)	—			600,000
		632,900			1,154,000
	Less amounts due within one year	—			60,000
	Less unamortized debt discount	442			459
	Total Energen	$	632,458		$	1,093,541
Maturities of Long-term Debt	'
	The aggregate maturities of Energen’s long-term debt outstanding at September 30, 2014 are as follows:
	(in thousands)
	Remaining 2014	2015	2016	2017	2018	2019 and thereafter
	—	—	—	$19,000	—	$613,900
Summary of Credit Facilities	'
	The following is a summary of information relating to Energen’s credit facilities:
	(in thousands)	September 30, 2014			December 31, 2013
	Notes payable to banks	$	78,900		$	489,000
	Available for borrowings	1,421,100			761,000
	Total	$	1,500,000		$	1,250,000
	Maximum amount outstanding at any month-end	$	750,000		$	901,000
	Average daily amount outstanding	$	559,878		$	804,895
	Weighted average interest rates based on:
	Average daily amount outstanding	1.43		%	1.38		%
	Amount outstanding at period-end	1.66		%	1.32		%

Reconciliation_of_Earnings_Per1

Reconciliation of Earnings Per Share (EPS) (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Schedule of Earnings Per Share Reconciliation	'
		Three months ended							Three months ended
	(in thousands, except per share amounts)	September 30, 2014							September 30, 2013
		Net				Per Share			Net				Per Share
		Income			Shares	Amount			Income			Shares	Amount
	Basic EPS	$	457,251		73,093	$	6.26		$	(19,298	)	72,346	$	(0.27	)
	Effect of dilutive securities
	Stock options				231							—
	Non-vested restricted stock				68							—
	Performance share awards				115							—
	Diluted EPS	$	457,251		73,507	$	6.22		$	(19,298	)	72,346	$	(0.27	)
	In periods of loss, shares that otherwise would have been included in diluted average common shares outstanding are excluded. The Company had 242,560 of excluded shares for the three months ended September 30, 2013.
		Nine months ended							Nine months ended
	(in thousands, except per share amounts)	September 30, 2014							September 30, 2013
		Net				Per Share			Net				Per Share
		Income			Shares	Amount			Income			Shares	Amount
	Basic EPS	$	502,614		72,861	$	6.9		$	120,461		72,220	$	1.67
	Effect of dilutive securities
	Stock options				219							41
	Non-vested restricted stock				67							10
	Performance share awards				91							1
	Diluted EPS	$	502,614		73,238	$	6.86		$	120,461		72,272	$	1.67
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	'
	Energen had the following shares that were excluded from the computation of diluted EPS, as inclusion would be anti-dilutive:
		Three months ended				Nine months ended
		September 30,				September 30,
	(in thousands)	2014		2013		2014		2013
	Stock options	6		—		6		875
	Performance share awards	2		—		4		79

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Pension Plans	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs	'
	The components of net periodic benefit cost for Energen’s defined benefit non-contributory pension plan and certain nonqualified supplemental pension plans were as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	1,902		$	1,326		$	5,157		$	3,980
	Interest cost	1,157			1,093			3,974			3,269
	Expected long-term return on assets	(1,157		)	(1,321		)	(4,067		)	(3,966		)
	Actuarial loss	1,296			1,760			4,115			5,417
	Prior service cost amortization	63			62			177			185
	Settlement charge	370			18			4,043			161
	Net periodic expense	$	3,631		$	2,938		$	13,399		$	9,046
Postretirement Benefit Plans	'
Defined Benefit Plan Disclosure [Line Items]	'
Schedule of Net Benefit Costs	'
	The components of net periodic postretirement benefit expense for Energen’s postretirement benefit plan were as follows:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	87		$	111		$	206		$	334
	Interest cost	137			175			587			526
	Expected long-term return on assets	(246		)	(212		)	(1,016		)	(638		)
	Actuarial gain	(151		)	—			(572		)	—
	Transition amortization	9			63			39			189
	Net periodic (income) expense	$	(164	)	$	137		$	(756	)	$	411

Exploratory_Costs_Tables

Exploratory Costs (Tables)	9 Months Ended
	Sep. 30, 2014
Extractive Industries [Abstract]	'
Schedule of Capitalized Exploratory Wells	'
	The following table sets forth capitalized exploratory well costs and includes additions pending determination of proved reserves, reclassifications to proved reserves and costs charged to expense:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Capitalized exploratory well costs at beginning of period	$	166,458		$	72,172		$	57,600		$	79,791
	Additions pending determination of proved reserves	258,724			99,428			623,913			319,008
	Reclassifications due to determination of proved reserves	(258,123		)	(112,821		)	(513,263		)	(340,020		)
	Exploratory well costs charged to expense	(1,217		)	—			(2,408		)	—
	Capitalized exploratory well costs at end of period	$	165,842		$	58,779		$	165,842		$	58,779
	The following table sets forth capitalized exploratory wells costs and includes amounts capitalized for a period greater than one year:
	(in thousands)	September 30, 2014			December 31, 2013
	Exploratory wells in progress	$	29,059		$	14,794
	Capitalized exploratory well costs capitalized for a period of one year or less	136,783			42,481
	Capitalized exploratory well costs for a period greater than one year	—			1,206
	Total capitalized exploratory well costs	$	165,842		$	58,481

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation Disclosure [Abstract]	'
Schedule of Change in Asset Retirement Obligation	'
	The following table reflects the components of the change in Energen’s ARO balance for the nine months ended September 30, 2014:
	(in thousands)
	Balance as of December 31, 2013	$	108,533
	Liabilities incurred	2,265
	Liabilities settled	(1,017		)
	Accretion expense	5,650
	Balance as of September 30, 2014	$	115,431

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	The following table provides changes in the components of accumulated other comprehensive income (loss), net of the related income tax effects.
	(in thousands)	Cash Flow Hedges			Pension and Postretirement Plans			Total
	Balance as of December 31, 2013	$	12,178		$	(32,245	)	$	(20,067	)
	Other comprehensive loss before reclassifications	(258		)	(1,784		)	(2,042		)
	Amounts reclassified from accumulated other comprehensive income (loss)	(8,302		)	7,716			(586		)
	Change in accumulated other comprehensive income (loss)	(8,560		)	5,932			(2,628		)
	Balance as of September 30, 2014	$	3,618		$	(26,313	)	$	(22,695	)
Reclassification out of Accumulated Other Comprehensive Income	'
	The following table provides details of the reclassifications out of accumulated other comprehensive income (loss).
		Three months ended			Three months ended
		30-Sep-14			30-Sep-13
	(in thousands)	Amounts Reclassified						Line Item Where Presented
	Gains (losses) on cash flow hedges:
	Commodity contracts	$	5,992		$	8,433		Gain (loss) on derivative instruments, net
	Interest rate swap	(247		)	(446		)	Interest expense
	Total cash flow hedges	5,745			7,987
	Income tax expense	(2,191		)	(3,048		)
	Net of tax	3,554			4,939
	Pension and postretirement plans:
	Transition obligation	2			(74		)	General and administrative
	Prior service cost	(74		)	(78		)	General and administrative
	Actuarial losses*	(1,060		)	(2,036		)	General and administrative
	Actuarial losses on settlement charges	(370		)	—			General and administrative
	Actuarial losses on settlement charges*	—			(46		)	Assets held for sale with prior period comparable
	Total pension and postretirement plans	(1,502		)	(2,234		)
	Income tax expense	525			783
	Net of tax	(977		)	(1,451		)
	Total reclassifications for the period	$	2,577		$	3,488
		Nine months ended			Nine months ended
		30-Sep-14			30-Sep-13
	(in thousands)	Amounts Reclassified						Line Item Where Presented
	Gains (losses) on cash flow hedges:
	Commodity contracts	$	15,781		$	30,226		Gain (loss) on derivative instruments, net
	Interest rate swap	(2,280		)	(1,282		)	Interest expense
	Total cash flow hedges	13,501			28,944
	Income tax expense	(5,199		)	(11,037		)
	Net of tax	8,302			17,907
	Pension and postretirement plans:
	Transition obligation	(17		)	(220		)	General and administrative
	Prior service cost	(222		)	(235		)	General and administrative
	Actuarial losses*	(3,640		)	(6,387		)	General and administrative
	Actuarial losses on settlement charges	(7,992		)	—			General and administrative
	Actuarial losses on settlement charges*	—			(421		)	Assets held for sale with prior period comparable
	Total pension and postretirement plans	(11,871		)	(7,263		)
	Income tax expense	4,155			2,542
	Net of tax	(7,716		)	(4,721		)
	Total reclassifications for the period	$	586		$	13,186
	* In the first quarter of 2013, Energen incurred a settlement charge of $0.5 million for the payment of lump sums from the nonqualified supplemental retirement plans, of which $0.1 million was recognized in actuarial losses above and $0.4 million was recognized as a regulatory asset at Alagasco and reported in actuarial losses on settlement charges above. In the third quarter of 2013, Energen incurred a settlement charge of $64,000 for the payment of lump sums from the nonqualified supplemental retirement plans, of which $18,000 is recognized in actuarial losses above and $46,000 was recognized as a regulatory asset at Alagasco and reported in actuarial losses on settlement charges above.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Schedule of Discontinued Operations	'
	The table below provides a detail of these items included in income (loss) from discontinued operations at September 30, 2014:
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands)	2014			2013			2014			2013
	Alagasco net income (loss)	$	(1,767	)	$	(8,961	)	$	40,646		$	37,557
	Depreciation, depletion and amortization	(103		)	(150		)	(408		)	(443		)
	General and administrative	1,710			1,158			3,337			4,784
	Interest expense	(4,329		)	(3,676		)	(17,306		)	(9,786		)
	Other income	—			(409		)	(347		)	(882		)
	Income tax expense	1,029			1,145			5,567			2,392
	Alagasco income (loss) from discontinued operations	(3,460		)	(10,893		)	31,489			33,622
	Energen income (loss) from discontinued operations	(25		)	1,866			(1,054		)	6,269
	Income (loss) from discontinued operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891
	The following table details held for sale properties by major classes of assets and liabilities:
	(in thousands)	31-Dec-13
		Alabama Gas Corporation			Black Warrior Basin			North Louisiana/East Texas			Total
	Cash	$	3,032		$	—		$	—		$	3,032
	Accounts receivable*	103,748			2,829			1,272			107,849
	Inventories	41,200			—			68			41,268
	Oil and gas properties	—			—			348,379			348,379
	Less accumulated depreciation, depletion and amortization	—						(301,609		)	(301,609		)
	Utility plant	1,491,433			—			—			1,491,433
	Less accumulated depreciation	(605,924		)	—			—			(605,924		)
	Other property, net	41			—			165			206
	Other current assets*	29,458			—			—			29,458
	Other long-term assets	128,780			—			—			128,780
	Total assets held for sale	1,191,768			2,829			48,275			1,242,872
	Accounts payable	(48,653		)	(1,732		)	(11		)	(50,396		)
	Royalty payable	—			(550		)	(869		)	(1,419		)
	Accrued taxes	(28,027		)	—			—			(28,027		)
	Notes payable to banks	(50,000		)	—			—			(50,000		)
	Other current liabilities*	(105,013		)	(379		)	(21		)	(105,413		)
	Other long-term liabilities	(331,409		)	—			(14,983		)	(346,392		)
	Long-term debt	(249,923		)	—			—			(249,923		)
	Total liabilities held for sale	(813,025		)	(2,661		)	(15,884		)	(831,570		)
	Total net assets held for sale	$	378,743		$	168		$	32,391		$	411,302
	*At December 31, 2013, Alagasco’s accounts receivable included a consolidating adjustment of $4.7 million to adjust for affiliated companies receivables. Certain other current assets and other current liabilities at Alagasco of $1.6 million and $0.5 million, respectively, were reclassified to continuing operations at Energen.
		Three months ended						Nine months ended
		September 30,						September 30,
	(in thousands, except per share data)	2014			2013			2014			2013
	Natural gas distribution revenues	$	39,874		$	48,368		$	397,648		$	390,567
	Oil and natural gas revenues	6			18,258			5,217			55,483
	Total revenues	$	39,880		$	66,626		$	402,865		$	446,050
	Pretax income (loss) from discontinued operations	$	(5,938	)	$	(14,677	)	$	48,581		$	64,098
	Income tax expense (benefit)	(2,453		)	(5,650		)	18,146			24,207
	Income (Loss) From Discontinued Operations	$	(3,485	)	$	(9,027	)	$	30,435		$	39,891
	Gain (loss) on disposal of discontinued operations	$	726,410		$	(24,612	)	$	724,743		$	(24,612	)
	Income tax expense (benefit)	286,305			(8,934		)	285,688			(8,934		)
	Gain (Loss) on Disposal of Discontinued Operations	$	440,105		$	(15,678	)	$	439,055		$	(15,678	)
	Total Income (Loss) From Discontinued Operations	$	436,620		$	(24,705	)	$	469,490		$	24,213
	Diluted Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	5.99			(0.22		)	5.99			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.94		$	(0.34	)	$	6.41		$	0.34
	Basic Earnings Per Average Common Share
	Income (loss) from discontinued operations	$	(0.05	)	$	(0.12	)	$	0.42		$	0.55
	Gain (loss) on disposal of discontinued operations	6.03			(0.22		)	6.03			(0.21		)
	Total Income (Loss) From Discontinued Operations	$	5.98		$	(0.34	)	$	6.45		$	0.34

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Details) (Alabama Gas Corporation, USD $)	0 Months Ended
	Aug. 31, 2014	Aug. 31, 2014
Alabama Gas Corporation	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'
Amount of consideration received	'	$1,600,000,000
Amount of debt assumed	267,000,000	'
Proceeds from sale	$1,320,000,000	'

Organization_and_Basis_of_Pres3

Organization and Basis of Presentation - Derivative Gains and Losses (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Gain (loss) on derivative instruments, net	$147,735	($88,192)	$9,498	($51,904)
Commodity contracts	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Open non-cash mark-to-market gains (losses) on derivative instruments	147,287	-63,560	53,985	-48,459
Closed gains (losses) on derivative instruments	448	-24,632	-44,487	-3,445
Gain (loss) on derivative instruments, net	$147,735	($88,192)	$9,498	($51,904)

Organization_and_Basis_of_Pres4

Organization and Basis of Presentation - Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Income (Loss) From Discontinued Operations	$436,620	($24,705)	$469,490	$24,213
Income (Loss) From Discontinued Operations	-3,485	-9,027	30,435	39,891
Alabama Gas Corporation	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Alagasco net income (loss)	-1,767	-8,961	40,646	37,557
Depreciation, depletion and amortization	-103	-150	-408	-443
General and administrative	1,710	1,158	3,337	4,784
Interest expense	-4,329	-3,676	-17,306	-9,786
Other income	0	-409	-347	-882
Income tax expense	1,029	1,145	5,567	2,392
Income (Loss) From Discontinued Operations	-3,460	-10,893	31,489	33,622
Parent Company	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Income (Loss) From Discontinued Operations	($25)	$1,866	($1,054)	$6,269

Derivative_Commodity_Instrumen2

Derivative Commodity Instruments - Commodity Contracts by Business Segment (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
	counterparty		counterparty		bbl	bbl
Derivative [Line Items]	'	'	'	'	'	'
Gain (Loss) on fair value of derivatives	$147,735	($88,192)	$9,498	($51,904)	'	'
Counterparties with whom company holds net gain positions	13	'	13	'	'	'
Counterparties with whom company holds net loss positions	1	'	1	'	'	'
Derivatives Transferred to Not Designated as Hedging Instruments	'	'	'	'	2,353,000	5,078,000
Commodity contracts	'	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'	'
Gain (Loss) on fair value of derivatives	147,735	-88,192	9,498	-51,904	'	'
Commodity contracts | J.P Morgan Ventures	'	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'	'
Gain (Loss) on fair value of derivatives	'	'	8,500	'	'	'
Commodity contracts | J Aron and Company	'	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'	'
Gain (Loss) on fair value of derivatives	'	'	4,400	'	'	'
Commodity contracts | Bank of Montreal	'	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'	'
Gain (Loss) on fair value of derivatives	'	'	$3,700	'	'	'

Derivative_Commodity_Instrumen3

Derivative Commodity Instruments - Offsetting Assets and Liabilities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	$43,620,000	$44,215,000
Gross Amounts Offset in the Balance Sheets	-7,667,000	-21,313,000
Total assets	35,953,000	22,902,000
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	35,953,000	22,902,000
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	9,115,000	51,615,000
Gross Amounts Offset in the Balance Sheets	-7,667,000	-21,313,000
Net Amount Presented in the Balance Sheets	1,448,000	30,302,000
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	1,448,000	30,302,000
Total Derivatives	34,505,000	-7,400,000
Net deferred tax liability	2,200,000	8,200,000
Current Assets	'	'
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	37,039,000	36,223,000
Gross Amounts Offset in the Balance Sheets	-6,844,000	-18,760,000
Total assets	30,195,000	17,463,000
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	30,195,000	17,463,000
Noncurrent Assets	'	'
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	6,581,000	7,992,000
Gross Amounts Offset in the Balance Sheets	-823,000	-2,553,000
Total assets	5,758,000	5,439,000
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	5,758,000	5,439,000
Current Liabilities	'	'
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	7,652,000	49,062,000
Gross Amounts Offset in the Balance Sheets	-6,844,000	-18,760,000
Net Amount Presented in the Balance Sheets	808,000	30,302,000
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	808,000	30,302,000
Noncurrent Liabilities	'	'
Derivative assets	'	'
Gross Amounts Recognized at Fair Value	1,463,000	2,553,000
Gross Amounts Offset in the Balance Sheets	-823,000	-2,553,000
Net Amount Presented in the Balance Sheets	640,000	0
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	$640,000	$0

Derivative_Commodity_Instrumen4

Derivative Commodity Instruments Derivatives commodity instruments - Cash flow hedging relationship in financial statements (Details) (Commodity contracts, USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Net gain (loss) recognized in other comprehensive income on derivatives (effective portion), net of tax	$29	$69	$40	($10,882)
Gain (Loss) Recognized in other comprehensive income on derivatives	18	42	25	-6,669
Gain (loss) on derivative instruments, net	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Gain reclassified from accumulated other comprehensive income into income (effective portion)	5,992	8,455	15,781	29,391
Gain (Loss) recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	$0	($22)	$0	$835

Derivative_Commodity_Instrumen5

Derivative Commodity Instruments Derivative Commodity instruments not designated as hedging instruments on the Income Statement (Details) (Gain (loss) on derivative instruments, net, USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Gain (loss) on derivative instruments, net	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Open non-cash mark-to-market gains (losses) on derivative instruments	$141,743	($92,313)	($6,283)	($70,735)

Derivative_Commodity_Instrumen6

Derivative Commodity Instruments Derivative Commodity - Reclassification (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivatives, Fair Value [Line Items]	'	'	'	'
Reclassification from comprehensive income, net of tax	'	'	$3,600,000	'
Revenue, Net	-497,761,000	-272,038,000	-1,065,136,000	-875,350,000
Production Period, Year One | NYMEX Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	2,502,000	'	2,502,000	'
Average contract price	'	'	92.66	'
Production Period, Year One | NYMEX Swaps | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	2,600,000	'	2,600,000	'
Average contract price ($ per Mcf)	'	'	4.57	'
Production Period, Year One | WTS/WTI Basis Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	300,000	'	300,000	'
Average contract price	'	'	-3.3	'
Production Period, Year One | WTI/WTI Basis Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	600,000	'	600,000	'
Average contract price	'	'	-3.08	'
Production Period, Year One | Liquids Swaps | Natural Gas Liquids	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	18,500,000	'	18,500,000	'
Average contract price	'	'	0.93	'
Production Period, Year One | Basin Specific Swaps, San Juan | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	7,580,000	'	7,580,000	'
Average contract price ($ per Mcf)	'	'	4.62	'
Production Period, Year One | Basin Specific Swaps - Permain | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	2,600,000	'	2,600,000	'
Average contract price ($ per Mcf)	'	'	3.81	'
Production Period, Year One | San Juan Basis Swaps | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	1.48	'	1.48	'
Average contract price ($ per Mcf)	'	'	-0.09	'
Production Period, Year One | Permian Basis Swaps | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	0.6	'	0.6	'
Average contract price ($ per Mcf)	'	'	-0.17	'
Production Period, Year Two | NYMEX Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	8,280,000	'	8,280,000	'
Average contract price	'	'	89.3	'
Production Period, Year Two | WTS/WTI Basis Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	2,160,000	'	2,160,000	'
Average contract price	'	'	-4.3	'
Production Period, Year Two | WTI/WTI Basis Swaps | Crude Oil	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	6,120,000	'	6,120,000	'
Average contract price	'	'	-5.11	'
Production Period, Year Two | Basin Specific Swaps, San Juan | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	23,000,000	'	23,000,000	'
Average contract price ($ per Mcf)	'	'	4.13	'
Production Period, Year Two | Basin Specific Swaps - Permain | Natural Gas	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Total Hedged Volumes	6,000,000	'	6,000,000	'
Average contract price ($ per Mcf)	'	'	4.2	'
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain from Discontinued Hedge Accounting	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Revenue, Net	'	'	$1,700,000	'

Fair_Value_Measurements_Recurr

Fair Value Measurements - Recurring Basis (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Noncurrent derivative instruments	$5,758	$5,439
Total assets	35,953	22,902
Total liabilities	-1,448	-30,302
Recurring	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Derivative instruments	30,195	17,463
Noncurrent derivative instruments	5,758	5,439
Total assets	35,953	22,902
Derivative instruments	-808	-30,302
Noncurrent derivative instruments	-640	'
Total liabilities	-1,448	-30,302
Net derivative asset	34,505	-7,400
Recurring | Level 2	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Derivative instruments	16,355	-1,658
Noncurrent derivative instruments	4,763	4,383
Total assets	21,118	2,725
Derivative instruments	-1,499	-28,414
Noncurrent derivative instruments	0	'
Total liabilities	-1,499	-28,414
Net derivative asset	19,619	-25,689
Recurring | Level 3	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Derivative instruments	13,840	19,121
Noncurrent derivative instruments	995	1,056
Total assets	14,835	20,177
Derivative instruments	691	-1,888
Noncurrent derivative instruments	-640	'
Total liabilities	51	-1,888
Net derivative asset	$14,886	$18,289

Change_in_Fair_Value_Details

- Change in Fair Value (Details) (Derivative Commodity Instruments, USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Commodity Instruments	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'	'	'
Mark-to-market gain included in earnings, unrealized	$12,200,000	'	$9,600,000	'
Mark-to-market loss included in earnings, unrealized	'	800,000	'	4,700,000
Balance at beginning of period	5,207,000	51,131,000	18,289,000	89,019,000
Realized gains	10,769,000	10,852,000	8,581,000	41,952,000
Unrealized gain (losses) relating to instruments held at the reporting date	9,348,000	-10,947,000	-3,734,000	-48,835,000
Settlements during period	-10,438,000	-9,830,000	-8,250,000	-40,930,000
Balance at end of period	$14,886,000	$41,206,000	$14,886,000	$41,206,000

Level_3_Measurements_of_Deriva

- Level 3 Measurements of Derivative Commodity Instruments (Details) (USD $)

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Level 3

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Discounted Cash Flow Valuation Technique

Commodity contracts

Commodity contracts

Commodity contracts

Commodity contracts

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Oil Basis - WTS/WTI

Oil Basis - WTS/WTI

Oil Basis - WTS/WTI

Oil Basis - WTS/WTI

Oil Basis - WTI/WTI

Oil Basis - WTI/WTI

Oil Basis - WTI/WTI

Oil Basis - WTI/WTI

Oil Basis - WTI/WTI

Oil Basis - WTI/WTI

Liquids Swaps

Liquids Swaps

Liquids Swaps

Natural Gas Basis - San Juan

Natural Gas Basis - San Juan

Natural Gas Basis - San Juan

Natural Gas Basis - San Juan

Natural Gas Basis - San Juan

Natural Gas Basis - San Juan

Natural Gas Basis - Permian

Natural Gas Basis - Permian

Natural Gas Basis - Permian

Natural Gas Basis - Permian

2014

2015

2015

2015

2014

2014

2014

2015

2015

2015

2014

2014

2014

2014

2014

2014

2015

2015

2015

2014

2014

2014

2015

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Fair Value Inputs, Derivatives, Quantitative Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain (Loss) Recognized in other comprehensive income on derivatives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$18,000

$42,000

$25,000

($6,669,000)

Sensitivity Analysis of Fair Value of 10 Percent Change in Commodity Prices

'

'

13,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sensitivity Analysis of Fair Value of Impact of 10 Percent Change in Mark-To-Market Derivative Contracts1

'

'

13,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative assets

35,953,000

22,902,000

'

1,115,000

'

'

'

2,736,000

'

'

'

'

'

1,600,000

'

'

4,946,000

'

'

5,097,000

'

'

'

'

'

1,924,000

'

'

'

'

Derivative liabilities

($1,448,000)

($30,302,000)

'

'

($181,000)

'

'

'

'

'

($1,979,000)

'

'

'

'

'

'

'

'

'

'

'

($372,000)

'

'

'

'

'

'

'

Fair Value Inputs, Price Per Barrel

'

'

'

6.62

'

4.2

4.24

'

7.07

7.18

'

4.6

4.97

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Inputs, Price Per Gallon

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.67

0.9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Inputs, Price Per Cubic Foot

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.05

0.12

'

0.09

0.1

'

0.09

0.1

0.13

'

'

'

'

Fair_Value_Measurements_Narrat

Fair Value Measurements -Narratives (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Long-term debt fair value	$637,300,000	$1,161,900,000
Reported Value Measurement	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Long-term debt fair value	632,900,000	1,154,000,000
Credit facility | Swap	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Face amount	150,000,000	'
Interest rate	1.04%	'
Credit facility | Swap | Level 2	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Interest rate cash flow hedge liability at fair value	$1,000,000	$1,800,000

LongTerm_Debt_and_Notes_Payabl2

Long-Term Debt and Notes Payable - Long-Term Debt (Details) (USD $)

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

In Thousands, unless otherwise specified

Credit facility

Credit facility

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Medium-term Notes

Notes Payable

Notes Payable

Senior Term Loans

Senior Term Loans

London Interbank Offered Rate (LIBOR)

7.40% Medium-term Notes, Series A, due July 24, 2017

7.40% Medium-term Notes, Series A, due July 24, 2017

7.36% Medium-term Notes, Series A, due July 24, 2017

7.36% Medium-term Notes, Series A, due July 24, 2017

7.23% Medium-term Notes, Series A, due July 28, 2017

7.23% Medium-term Notes, Series A, due July 28, 2017

7.32% Medium-term Notes, Series A, due July 28, 2022

7.32% Medium-term Notes, Series A, due July 28, 2022

7.60% Medium-term Notes, Series A, due July 26, 2027

7.60% Medium-term Notes, Series A, due July 26, 2027

7.35% Medium-term Notes, Series A, due July 28, 2027

7.35% Medium-term Notes, Series A, due July 28, 2027

7.125% Medium-term Notes, Series B, due February 15, 2028

7.125% Medium-term Notes, Series B, due February 15, 2028

4.625% Notes, due September 1, 2021

4.625% Notes, due September 1, 2021

Senior Term Loans, (floating rate interest LIBOR plus 1.625%)

Senior Term Loans, (floating rate interest LIBOR plus 1.625%)

Senior Term Loans

Senior Term Loans, (floating rate interest LIBOR plus 1.625%)

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross amount

$632,900

$1,154,000

$78,900

$0

$2,000

$2,000

$15,000

$15,000

$2,000

$2,000

$20,000

$20,000

$5,000

$5,000

$10,000

$10,000

$100,000

$100,000

$400,000

$400,000

$0

$600,000

'

Less amounts due within one year

0

60,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Less unamortized debt discount

442

459

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long-term debt

$632,458

$1,093,541

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Rate

'

'

'

'

7.40%

'

7.36%

'

7.23%

'

7.32%

'

7.60%

'

7.35%

'

7.13%

'

4.63%

'

'

'

'

Floating rate interest spread

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.63%

LongTerm_Debt_and_Notes_Payabl3

Long-Term Debt and Notes Payable - Maturities of Long-Term Debt (Details) (USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]	'
Remaining 2014	$0
2015	0
2016	0
2017	19,000
2018	0
2019 and thereafter	$613,900

LongTerm_Debt_and_Notes_Payabl4

Long-Term Debt and Notes Payable - Credit Facilities (Details) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]	'	'
Notes payable to banks	$78,900	$489,000
Available for borrowings	1,421,100	761,000
Total Energen	1,500,000	1,250,000
Maximum amount outstanding at any month-end	750,000	901,000
Average daily amount outstanding	$559,878	$804,895
Average daily amount outstanding interest rate	1.43%	1.38%
Amount outstanding at period-end interest rate	1.66%	1.32%

LongTerm_Debt_and_Notes_Payabl5

Long-Term Debt and Notes Payable - Narratives (Details) (USD $)	3 Months Ended		9 Months Ended				0 Months Ended		0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2013	Sep. 02, 2014	Sep. 02, 2014	Oct. 30, 2012
						Senior Loans	Syndicated Credit Facility	Syndicated Credit Facility	Syndicated Credit Facility
						Senior Term Loans due March 31, 2014 to December 17, 2017	Credit Facility, September 2, 2014	Credit Facility, September 2, 2014	Credit Facility, October 30, 2012
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'	'
Senior terms loan	'	'	'	'	'	$600,000,000	'	'	'
Cross default provision, threshold amount	10,000,000	'	10,000,000	'	'	'	'	'	'
Maximum borrowing capacity	'	'	'	'	'	'	'	1,500,000,000	1,250,000,000
Debt Instrument, Term	'	'	'	'	'	'	'5 years	'	'5 years
Initial borrowing base	1,500,000,000	'	1,500,000,000	'	1,250,000,000	'	'	2,100,000,000	'
Credit facility cross default provision, threshold amount	75,000,000	'	75,000,000	'	'	'	'	'	'
Interest expense	11,522,000	10,149,000	27,374,000	30,232,000	'	'	'	'	'
Capitalized interest expense	$0	$0	$37,000	$200,000	'	'	'	'	'
Debt covenant, Debt to EBITDAX Ratio	'	'	'	'	'	'	'	4	'
Debt covenant, Current assets to Current Liabilities Ratio	'	'	'	'	'	'	'	1	'
Debt covenant, Minimum net present value of proved reserves to consolidated debt, Ratio	'	'	'	'	'	'	'	1.5	'
Percent, Loan Limit	'	'	'	'	'	'	'	10.00%	'

Reconciliation_of_Earnings_Per2

Reconciliation of Earnings Per Share (EPS) - Earnings Per Share Reconciliation (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share Reconciliation	'	'	'	'
Net Income, Basic EPS	$457,251	($19,298)	$502,614	$120,461
Basic Shares Outstanding (in shares)	73,093	72,346	72,861	72,220
Earnings Per Share, Basic (in dollars per share)	$6.26	($0.27)	$6.90	$1.67
Effect of dilutive securities	'	'	'	'
Net Income, Diluted EPS	$457,251	($19,298)	$502,614	$120,461
Diluted Shares Outstanding (in shares)	73,507	72,346	73,238	72,272
Earnings Per Share, Diluted (dollars per share)	$6.22	($0.27)	$6.86	$1.67
Stock options	'	'	'	'
Effect of dilutive securities	'	'	'	'
Incremental common shares attributable to share-based payment arrangements	231	0	219	41
Non-vested restricted stock	'	'	'	'
Effect of dilutive securities	'	'	'	'
Incremental common shares attributable to share-based payment arrangements	68	0	67	10
Performance share awards	'	'	'	'
Effect of dilutive securities	'	'	'	'
Incremental common shares attributable to share-based payment arrangements	0	0	91	1

Reconciliation_of_Earnings_Per3

Reconciliation of Earnings Per Share (EPS) - Antidilutive Securities (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	242,560	'	'	'
Stock options	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	6,000	0	6,000	875,000
Performance share awards	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	2,000	0	4,000	79,000

Stock_Compensation_Details

Stock Compensation (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Thousands, except Share data, unless otherwise specified

Jun. 30, 2014

Mar. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Jan. 31, 2013

Jun. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Mar. 31, 2014

Mar. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Mar. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Stock options

Stock options

Stock options

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Performance share awards

Stock Appreciation Rights (SARs)

Stock Appreciation Rights (SARs)

Stock Appreciation Rights (SARs)

Deferred Compensation

Deferred Compensation

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Petrotech Incentive Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Stock Compensation Plan

Petrotech Incentive Plan

Petrotech Incentive Plan

Petrotech Incentive Plan

Petrotech Incentive Plan

Petrotech Incentive Plan

Petrotech Incentive Plan

2 year vesting period

Vesting Period, Three [Member]

Vesting Period, Three [Member]

Vesting Period, Three [Member]

2 year vesting period

2 year vesting period

2 year vesting period

Vesting Period, Three [Member]

Vesting Period, Three [Member]

Vesting Period, Three [Member]

Vesting Period, Three [Member]

Vesting Period, Three [Member]

20 months vesting period

20 months vesting period

Share-based Compensation Arrangement by Share-based Payment Award

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'3 years

'2 years

'

'

'3 years

'

'

'

'2 years

'

'

'3 years

'

'

'

'3 years

'

'20 months

'

'

'3 years

'

'

Expiration period

'

'

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Grants in period, options

2,439

107,868

'

6,312

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Grants in period, options, fair value

$32.22

$27.57

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Grants in period (in shares)

'

'

'

'

41,664

928

'

36,920

650

287

'

1,467

63,842

'

'

28,840

9,728

'

596

'

'

62,749

'

'

'

Grant date fair value

'

'

'

$78.99

'

$79.15

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Grants in period, fair value (in dollars per share)

'

'

'

'

$70.68

'

'

$94.38

$137.11

$118.99

'

$109.02

$93.13

'

$72.06

'

'

'

$72.14

'

$28.71

'

'

'

'

Noncash payments for repurchase of common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$36

$400

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

1 Months Ended

Jan. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Mar. 31, 2014

Sep. 30, 2013

Mar. 31, 2013

Oct. 31, 2014

Pension Plans

Pension Plans

Pension Plans

Pension Plans

Pension Plans

Pension Plans

Pension Plans

Postretirement Benefit Plans

Postretirement Benefit Plans

Postretirement Benefit Plans

Postretirement Benefit Plans

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Subsequent Event

Pension Plans

Defined Benefit Plan Disclosure [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reclassification of Rabbi Trust investments

'

'

'

'

'

'

'

'

'

'

'

$17,100,000

'

'

'

'

Components of net periodic benefit cost:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Service cost

'

1,902,000

'

'

1,326,000

5,157,000

3,980,000

87,000

111,000

206,000

334,000

'

'

'

'

'

Interest cost

'

1,157,000

'

'

1,093,000

3,974,000

3,269,000

137,000

175,000

587,000

526,000

'

'

'

'

'

Expected long-term return on assets

'

-1,157,000

'

'

-1,321,000

-4,067,000

-3,966,000

-246,000

-212,000

-1,016,000

-638,000

'

'

'

'

'

Actuarial (Gain) Loss

'

1,296,000

'

'

1,760,000

4,115,000

5,417,000

-151,000

0

-572,000

0

'

'

'

'

'

Transition amortization

'

'

'

'

'

'

'

9,000

63,000

39,000

189,000

'

'

'

'

'

Prior service cost amortization

'

63,000

'

'

62,000

177,000

185,000

'

'

'

'

'

'

'

'

'

Settlement charge

'

370,000

'

'

18,000

4,043,000

161,000

'

'

'

'

'

'

18,000

'

'

Net periodic expense

'

3,631,000

'

'

2,938,000

13,399,000

9,046,000

-164,000

137,000

-756,000

411,000

'

'

'

'

'

Employer Contributions in Current Fiscal Year, Required Contributions

'

7,700,000

'

'

'

7,700,000

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Contributions by Employer

3,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10,000,000

Benefit payments made in current fiscal year

'

74,000

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

Estimated future benefit payments in current fiscal year

'

5,200,000

'

'

'

5,200,000

'

'

'

'

'

'

'

'

'

'

Settlement charges

'

'

'

'

'

'

'

'

'

'

'

0

400,000

64,000

500,000

'

Settlement charges expensed

'

300,000

400,000

6,900,000

'

'

'

'

'

'

'

'

'

'

100,000

'

Settlement charges in discontinued operations

'

'

'

$3,700,000

'

'

'

'

'

'

'

'

'

'

'

'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
	pit
Crude Oil and Natural Gas	'
Long-term Purchase Commitment [Line Items]	'
Oil And Gas Delivery Commitments And Contracts, Remaining Contractual Amount (BOE)	6,000
Mitchell County, Texas [Member]	'
Long-term Purchase Commitment [Line Items]	'
Environmental Exit Costs, Number of Sites	9
Environmental Exit Costs, Anticipated Cost	$4.10
Accrual for Environmental Loss Contingencies, Payments	$3.40

Commitments_and_Contingencies_1

Commitments and Contingencies - New Mexico Audits (Details) (Unfavorable Regulatory Action, USD $)	Sep. 30, 2014
Unfavorable Regulatory Action	'
Loss Contingencies [Line Items]	'
Minimum loss contingency range of loss	$129,700
Maximum loss contingency range of possible loss	$23,000,000

Exploratory_Costs_Details

Exploratory Costs (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
	well		well
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]	'	'	'	'	'
Capitalized exploratory well costs at beginning of period	$166,458	$72,172	$57,600	$79,791	'
Additions pending determination of proved reserves	258,724	99,428	623,913	319,008	'
Reclassifications due to determination of proved reserves	-258,123	-112,821	-513,263	-340,020	'
Exploratory well costs charged to expense	-1,217	0	-2,408	0	'
Capitalized exploratory well costs at end of period	165,842	58,779	165,842	58,779	'
Exploratory wells in progress	29,059	'	29,059	'	14,794
Capitalized exploratory well costs capitalized for a period of one year or less	136,783	'	136,783	'	42,481
Capitalized exploratory well costs for a period greater than one year	0	'	0	'	1,206
Total capitalized exploratory well costs	$165,842	'	$165,842	'	$58,481
Number of wells in process of drilling	56	'	56	'	'

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'	'	'
Balance as of December 31, 2013	'	'	$108,533	'
Liabilities incurred	'	'	2,265	'
Liabilities settled	'	'	-1,017	'
Accretion of discount on asset retirement obligations	1,924	1,771	5,650	5,187
Balance as of September 30, 2014	$115,431	'	$115,431	'

Rollforward_of_Accumulated_Oth

Rollforward of Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Balance as of December 31, 2013	($20,067)
Other comprehensive loss before reclassifications	-2,042
Amounts reclassified from accumulated other comprehensive income (loss)	-586
Change in accumulated other comprehensive income (loss)	-2,628
Balance as of September 30, 2014	-22,695
Cash Flow Hedges	'
Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Balance as of December 31, 2013	12,178
Other comprehensive loss before reclassifications	-258
Amounts reclassified from accumulated other comprehensive income (loss)	-8,302
Change in accumulated other comprehensive income (loss)	-8,560
Balance as of September 30, 2014	3,618
Pension and Postretirement Plans	'
Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'
Balance as of December 31, 2013	-32,245
Other comprehensive loss before reclassifications	-1,784
Amounts reclassified from accumulated other comprehensive income (loss)	7,716
Change in accumulated other comprehensive income (loss)	5,932
Balance as of September 30, 2014	($26,313)

Reclassifications_of_Accumulat

Reclassifications of Accumulated Other Comprehensive Income (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Mar. 31, 2014

Sep. 30, 2013

Mar. 31, 2013

Sep. 30, 2013

Mar. 31, 2013

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Pension and Postretirement Plans

Pension and Postretirement Plans

Pension and Postretirement Plans

Pension and Postretirement Plans

Commodity contracts

Commodity contracts

Commodity contracts

Commodity contracts

Interest rate swap

Interest rate swap

Interest rate swap

Interest rate swap

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Alabama Gas Corporation

Alabama Gas Corporation

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Cash Flow Hedges

Supplemental Employee Retirement Plan

Supplemental Employee Retirement Plan

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Reclassification out of Accumulated Other Comprehensive Income

Gains (losses) on cash flow hedges:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reclassification Adjustment from AOCI on Derivatives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5,992,000

$8,433,000

$15,781,000

$30,226,000

($247,000)

($446,000)

($2,280,000)

($1,282,000)

'

'

'

'

'

'

Total

'

'

'

'

'

'

'

'

5,745,000

7,987,000

13,501,000

28,944,000

-1,502,000

-2,234,000

-11,871,000

-7,263,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income tax expense

-16,055,000

-3,128,000

-23,287,000

-53,401,000

'

'

'

'

-2,191,000

-3,048,000

-5,199,000

-11,037,000

525,000

783,000

4,155,000

2,542,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net of tax

'

'

'

'

2,577,000

3,488,000

586,000

13,186,000

3,554,000

4,939,000

8,302,000

17,907,000

-977,000

-1,451,000

-7,716,000

-4,721,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pension and postretirement plans:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Transition obligation

'

'

'

'

'

'

'

'

'

'

'

'

2,000

-74,000

-17,000

-220,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prior service cost

'

'

'

'

'

'

'

'

'

'

'

'

-74,000

-78,000

-222,000

-235,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Actuarial losses

'

'

'

'

'

'

'

'

'

'

'

'

-1,060,000

-2,036,000

-3,640,000

-6,387,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Actuarial losses on settlement charges

'

'

'

'

'

'

'

'

'

'

'

'

'

0

-7,992,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Actuarial losses on settlement charges

'

'

'

'

'

'

'

'

'

'

'

'

-370,000

-46,000

0

-421,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Settlement charges

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

400,000

64,000

500,000

'

'

Settlement charges expensed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100,000

'

'

Settlements recognized as a pension asset

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

46,000

400,000

Recognized in actuarial losses

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$18,000

'

'

'

Discontinued_Operations_Narrat

Discontinued Operations Narrative (Details) (USD $)

0 Months Ended

0 Months Ended

3 Months Ended

1 Months Ended

Sep. 02, 2014

Sep. 02, 2014

Oct. 30, 2012

Aug. 31, 2014

Aug. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Oct. 31, 2013

Dec. 31, 2012

Syndicated Credit Facility

Syndicated Credit Facility

Syndicated Credit Facility

Alabama Gas Corporation

Alabama Gas Corporation

North Louisiana and East Texas Natural Gas and Oil Properties

North Louisiana and East Texas Natural Gas and Oil Properties

North Louisiana and East Texas Natural Gas and Oil Properties

North Louisiana and East Texas Natural Gas and Oil Properties

North Louisiana and East Texas Natural Gas and Oil Properties

Black Warrior Basin Properties

Black Warrior Basin Properties

Credit Facility, September 2, 2014

Credit Facility, September 2, 2014

Credit Facility, October 30, 2012

Natural Gas

Oil

Alabama

Alabama

Mcf

MBbls

Natural Gas

Mcf

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Amount of consideration received

'

'

'

'

$1,600,000,000

'

'

'

'

'

'

'

Amount of debt assumed

'

'

'

267,000,000

'

'

'

'

'

'

'

'

Proceeds from sale

'

'

'

1,320,000,000

'

'

'

'

'

'

'

'

Sale price of gas and oil properties

'

'

'

'

'

30,300,000

'

'

'

'

'

'

Impairment of oil and gas properties held-for-sale

'

'

'

'

'

1,700,000

5,200,000

24,600,000

'

'

'

'

Proved Developed Reserves (Volume)

'

'

'

'

'

'

'

'

23,000,000

91

'

97,000,000

Proceeds from the sale of oil and gas property

'

'

'

'

'

'

'

'

'

'

160,000,000

'

Gain on disposition of oil and gas property

'

'

'

'

'

'

'

'

'

'

35,000,000

'

Maximum borrowing capacity

'

$1,500,000,000

$1,250,000,000

'

'

'

'

'

'

'

'

'

Debt Instrument, Term

'5 years

'

'5 years

'

'

'

'

'

'

'

'

'

Discontinued_Operations_Balanc

Discontinued Operations Balance Sheet and Income Statement (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Assets of Disposal Group, Including Discontinued Operation [Abstract]	'	'	'	'	'
Cash	'	'	'	'	$3,032,000
Accounts receivable	'	'	'	'	107,849,000
Inventories	'	'	'	'	41,268,000
Oil and gas properties	'	'	'	'	348,379,000
Less accumulated depreciation, depletion and amortization	'	'	'	'	-301,609,000
Utility plant	'	'	'	'	1,491,433,000
Less accumulated depreciation	'	'	'	'	-605,924,000
Other property, net	'	'	'	'	206,000
Other current assets	'	'	'	'	29,458,000
Other long-term assets	'	'	'	'	128,780,000
Total assets held for sale	'	'	'	'	1,242,872,000
Total assets held for sale	'	'	'	'	'
Accounts payable	'	'	'	'	-50,396,000
Royalty payable	'	'	'	'	-1,419,000
Accrued taxes	'	'	'	'	-28,027,000
Notes payable to banks	'	'	'	'	-50,000,000
Other current liabilities	'	'	'	'	-105,413,000
Other long-term liabilities	'	'	'	'	-346,392,000
Long-term debt	'	'	'	'	-249,923,000
Total liabilities held for sale	'	'	'	'	-831,570,000
Total net assets held for sale	'	'	'	'	411,302,000
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]	'	'	'	'	'
Natural gas distribution revenues	39,874,000	48,368,000	397,648,000	390,567,000	'
Oil and natural gas revenues	6,000	18,258,000	5,217,000	55,483,000	'
Total revenues	39,880,000	66,626,000	402,865,000	446,050,000	'
Pretax income (loss) from discontinued operations	-5,938,000	-14,677,000	48,581,000	64,098,000	'
Income tax expense (benefit)	-2,453,000	-5,650,000	18,146,000	24,207,000	'
Income (Loss) From Discontinued Operations	-3,485,000	-9,027,000	30,435,000	39,891,000	'
Gain (loss) on disposal of discontinued operations	726,410,000	-24,612,000	724,743,000	-24,612,000	'
Income tax expense (benefit)	286,305,000	-8,934,000	285,688,000	-8,934,000	'
Gain (Loss) on Disposal of Discontinued Operations	440,105,000	-15,678,000	439,055,000	-15,678,000	'
Income (Loss) From Discontinued Operations	436,620,000	-24,705,000	469,490,000	24,213,000	'
Diluted Earnings Per Average Common Share	'	'	'	'	'
Income (Loss) from Discontinued Operations (in dollars per share)	($0.05)	($0.12)	$0.42	$0.55	'
Loss on Disposal of Discontinued Operations (in dollars per share)	$5.99	($0.22)	$5.99	($0.21)	'
Total Income (Loss) From Discontinued Operations (in dollars per share)	$5.94	($0.34)	$6.41	$0.34	'
Basic Earnings Per Average Common Share	'	'	'	'	'
Income (Loss) from Discontinued Operations (in dollars per share)	($0.05)	($0.12)	$0.42	$0.55	'
Loss on Disposal of Discontinued Operations (in dollars per share)	$6.03	($0.22)	$6.03	($0.21)	'
Total Income (Loss) From Discontinued Operations (in dollars per share)	$5.98	($0.34)	$6.45	$0.34	'
Adjustment for affiliated companies receivables	'	'	'	'	4,700,000
Reclassification from accrued taxes to other current assets	'	'	'	'	1,600,000
Reclassification from accrued taxes to other current liabilities	'	'	'	'	500,000
Alabama Gas Corporation	'	'	'	'	'
Assets of Disposal Group, Including Discontinued Operation [Abstract]	'	'	'	'	'
Cash	'	'	'	'	3,032,000
Accounts receivable	'	'	'	'	103,748,000
Inventories	'	'	'	'	41,200,000
Oil and gas properties	'	'	'	'	0
Less accumulated depreciation, depletion and amortization	'	'	'	'	0
Utility plant	'	'	'	'	1,491,433,000
Less accumulated depreciation	'	'	'	'	-605,924,000
Other property, net	'	'	'	'	41,000
Other current assets	'	'	'	'	29,458,000
Other long-term assets	'	'	'	'	128,780,000
Total assets held for sale	'	'	'	'	1,191,768,000
Total assets held for sale	'	'	'	'	'
Accounts payable	'	'	'	'	-48,653,000
Royalty payable	'	'	'	'	0
Accrued taxes	'	'	'	'	-28,027,000
Notes payable to banks	'	'	'	'	-50,000,000
Other current liabilities	'	'	'	'	-105,013,000
Other long-term liabilities	'	'	'	'	-331,409,000
Long-term debt	'	'	'	'	-249,923,000
Total liabilities held for sale	'	'	'	'	-813,025,000
Total net assets held for sale	'	'	'	'	378,743,000
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]	'	'	'	'	'
Income (Loss) From Discontinued Operations	-3,460,000	-10,893,000	31,489,000	33,622,000	'
Black Warrior Basin	'	'	'	'	'
Assets of Disposal Group, Including Discontinued Operation [Abstract]	'	'	'	'	'
Cash	'	'	'	'	0
Accounts receivable	'	'	'	'	2,829,000
Inventories	'	'	'	'	0
Oil and gas properties	'	'	'	'	0
Less accumulated depreciation, depletion and amortization	'	'	'	'	'
Utility plant	'	'	'	'	0
Less accumulated depreciation	'	'	'	'	0
Other property, net	'	'	'	'	0
Other current assets	'	'	'	'	0
Other long-term assets	'	'	'	'	0
Total assets held for sale	'	'	'	'	2,829,000
Total assets held for sale	'	'	'	'	'
Accounts payable	'	'	'	'	-1,732,000
Royalty payable	'	'	'	'	-550,000
Accrued taxes	'	'	'	'	0
Notes payable to banks	'	'	'	'	0
Other current liabilities	'	'	'	'	-379,000
Other long-term liabilities	'	'	'	'	0
Long-term debt	'	'	'	'	0
Total liabilities held for sale	'	'	'	'	-2,661,000
Total net assets held for sale	'	'	'	'	168,000
North Louisiana/East Texas	'	'	'	'	'
Assets of Disposal Group, Including Discontinued Operation [Abstract]	'	'	'	'	'
Cash	'	'	'	'	0
Accounts receivable	'	'	'	'	1,272,000
Inventories	'	'	'	'	68,000
Oil and gas properties	'	'	'	'	348,379,000
Less accumulated depreciation, depletion and amortization	'	'	'	'	-301,609,000
Utility plant	'	'	'	'	0
Less accumulated depreciation	'	'	'	'	0
Other property, net	'	'	'	'	165,000
Other current assets	'	'	'	'	0
Other long-term assets	'	'	'	'	0
Total assets held for sale	'	'	'	'	48,275,000
Total assets held for sale	'	'	'	'	'
Accounts payable	'	'	'	'	-11,000
Royalty payable	'	'	'	'	-869,000
Accrued taxes	'	'	'	'	0
Notes payable to banks	'	'	'	'	0
Other current liabilities	'	'	'	'	-21,000
Other long-term liabilities	'	'	'	'	-14,983,000
Long-term debt	'	'	'	'	0
Total liabilities held for sale	'	'	'	'	-15,884,000
Total net assets held for sale	'	'	'	'	$32,391,000

Acquisition_and_Disposition_of1

Acquisition and Disposition of Properties - Held for Sale (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2014
In Millions, unless otherwise specified	Natural Gas Basis - San Juan	Discontinued Operations, Held-for-sale or Disposed of by Sale	Discontinued Operations, Held-for-sale or Disposed of by Sale
	MBoe	Natural Gas Basis - Permian	Natural Gas Basis - San Juan
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Non-cash impairment writedown	'	$31.20	$147.90
Proved Developed Reserves (Energy)	73,070	'	'

Acquisition_and_Dispositions_o

Acquisition and Dispositions of Properties Narrative (Details) (San Juan, Subsequent Event, USD $)	1 Months Ended
In Millions, unless otherwise specified	Oct. 31, 2014
	acre
San Juan | Subsequent Event	'
Gas and Oil Acreage [Line Items]	'
Acres of unproved leasehold, Net	15,000
Payment for unproved leasehold	$22.80