Energen (EGN) 10-Q 9 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	May. 02, 2016
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Entity Registrant Name	ENERGEN CORP
Entity Central Index Key	277,595
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		97,069,395

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 35,806	$ 1,272
Accounts receivable, net	61,434	63,097
Inventories	12,185	11,255
Assets held for sale	183,234	93,739
Derivative instruments	18,810	56,963
Prepayments and other	21,772	20,014
Total current assets	333,241	246,340
Oil and natural gas properties, successful efforts method
Proved properties	7,491,304	7,611,118
Unproved properties	117,988	145,724
Less accumulated depreciation, depletion and amortization	3,611,302	3,454,510
Oil and natural gas properties, net	3,997,990	4,302,332
Other property and equipment, net	47,186	48,358
Total property, plant and equipment, net	4,045,176	4,350,690
Other postretirement assets	4,366	3,881
Noncurrent derivative instruments	148	0
Other assets	10,087	10,245
TOTAL ASSETS	4,393,018	4,611,156
Current Liabilities
Accounts payable	47,550	64,742
Accrued taxes	13,230	5,801
Accrued wages and benefits	9,127	28,563
Accrued capital costs	58,221	79,206
Revenue and royalty payable	56,949	60,493
Liabilities related to assets held for sale	14,102	12,789
Pension liabilities	0	15,685
Derivative instruments	5,468	459
Other	13,215	19,783
Total current liabilities	217,862	287,521
Long-term debt	551,147	773,550
Asset retirement obligations	90,223	89,990
Deferred income taxes	446,335	552,369
Noncurrent derivative instruments	273	0
Other long-term liabilities	10,718	11,866
Total liabilities	$ 1,316,558	$ 1,715,296
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; 100,126,767 shares and 81,770,161 shares issued at March 31, 2016 and December 31, 2015, respectively	1,001	818
Premium on capital stock	1,363,178	979,030
Retained earnings	1,842,900	2,046,016
Accumulated other comprehensive income (loss), net of tax
Pension and postretirement plans	2,066	263
Deferred compensation plan	2,246	1,965
Treasury stock, at cost; 3,122,759 shares and 3,026,350 shares at March 31, 2016 and December 31, 2015, respectively	(134,931)	(132,232)
Total shareholders’ equity	3,076,460	2,895,860
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,393,018	$ 4,611,156

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2016	Dec. 31, 2015
Shareholders’ Equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	100,126,767	81,770,161
Treasury stock, shares	3,122,759	3,026,350

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues
Oil, natural gas liquids and natural gas sales	$ 122,764	$ 187,822
Gain on derivative instruments, net	5,455	34,036
Total revenues	128,219	221,858
Operating Costs and Expenses
Oil, natural gas liquids and natural gas production	47,727	67,754
Production and ad valorem taxes	11,170	19,065
Depreciation, depletion and amortization	119,362	134,381
Asset impairment	220,025	6,583
Exploration	242	763
General and administrative (including non-cash stock based compensation of $2,471 and $5,080 for the three months ended March 31, 2016 and 2015, respectively)	29,525	32,055
Accretion of discount on asset retirement obligations	1,757	2,010
(Gain) loss on sale of assets and other	222	(28,344)
Total operating costs and expenses	430,030	234,267
Operating Loss	(301,811)	(12,409)
Other Income (Expense)
Interest expense	(9,833)	(11,758)
Other income	95	46
Total other expense	(9,738)	(11,712)
Loss Before Income Taxes	(311,549)	(24,121)
Income tax benefit	(108,433)	(8,701)
Net Loss	$ (203,116)	$ (15,420)
Diluted Earnings Per Average Common Share	$ (2.34)	$ (0.21)
Basic Earnings Per Average Common Share	$ (2.34)	$ (0.21)
Diluted Average Common Shares Outstanding (in shares)	86,632	72,830
Basic Average Common Shares Outstanding (in shares)	86,632	72,830
Dividends Per Common Share	$ 0	$ 0.02

Consolidated Statements of Inc5

Consolidated Statements of Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Non-cash stock based compensation	$ 2,471	$ 5,080

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Loss	$ (203,116)	$ (15,420)
Pension and postretirement plans:
Amortization of prior service cost, net of tax of ($47) and $0, respectively	(78)	0
Amortization of net loss, including settlement charges, net of tax of $1,168 and $996, respectively	1,890	1,851
Current period change in fair value of pension and postretirement plans, net of tax of ($6) and $0, respectively	(9)	0
Total pension and postretirement plans	1,803	1,851
Comprehensive Loss	$ (201,313)	$ (13,569)

Consolidated Statements of Com7

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Amortization of prior service cost, tax	$ (47)	$ 0
Amortization of net loss including settlement charges, tax	1,168	996
Current period change in fair value of pension and postretirement plans, tax	$ (6)	$ 0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net Loss	$ (203,116)	$ (15,420)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	119,362	134,381
Asset impairment	220,025	6,583
Accretion of discount on asset retirement obligations	1,757	2,010
Deferred income taxes	(107,149)	(16,009)
Change in derivative fair value	(5,151)	30,987
(Gain) loss on sale of assets	52	(28,502)
Stock-based compensation expense	2,471	5,080
Other, net	2,377	(10,944)
Net change in:
Accounts receivable	50,101	42,908
Inventories	(465)	(3,512)
Accounts payable	(19,611)	(11,814)
Accrued taxes/income tax receivable	2,179	13,633
Pension contributions	(14,516)	(10,872)
Other current assets and liabilities	(27,044)	4,493
Net cash provided by operating activities	21,272	143,002
Investing Activities
Additions to oil and natural gas properties	(137,296)	(395,317)
Acquisitions, net of cash acquired	(7,883)	(30,767)
Proceeds from the sale of assets	187	392,802
Purchase of short-term investments	0	(649,000)
Sale of short-term investments	0	340,000
Net cash used in investing activities	(144,992)	(342,282)
Financing Activities
Payment of dividends on common stock	0	(1,462)
Issuance of common stock, net	381,219	291
Net change in credit facility	(222,500)	200,000
Tax benefit on stock compensation	(465)	129
Net cash provided by financing activities	158,254	198,958
Net change in cash and cash equivalents	34,534	(322)
Cash and cash equivalents at beginning of period	1,272	1,852
Cash and cash equivalents at end of period	$ 35,806	$ 1,530

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2016
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 engaged in the exploration, development and production of oil, natural gas liquids and natural gas primarily in the Permian Basin in west Texas and the San Juan Basin in New Mexico. Headquartered in Birmingham, Alabama, our operations are conducted 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, 2015 , 2014 and 2013 , included in the 2015 Annual Report of Energen on Form 10-K. Our accompanying unaudited consolidated financial statements include Energen and its subsidiaries, principally Energen Resources, 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 a fair statement of 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. Certain reclassifications were made to conform prior periods’ financial statements to the current-quarter presentation. Liquidity At March 31, 2016, we had $35.8 million of cash on hand and $1.4 billion of committed financing available under our credit facility. On April 13, 2016, our committed financing available under our credit facility was reduced to $1.05 billion in association with our scheduled semi-annual redetermination. To finance our operations, working capital and capital spending, we expect to use internally generated cash flow from operations supplemented by our existing five-year syndicated credit facility. As discussed in Note 6, Equity Offering, during the first quarter of 2016, Energen issued 18,170,000 additional shares of common stock and received net proceeds of approximately $381.1 million , after deducting offering expenses. Energen may also issue long-term debt and additional equity periodically to replace short-term obligations, enhance liquidity and provide for permanent financing. Access to capital is an integral part of Energen’s business plan. As of March 31, 2016, the Company has $554.0 million outstanding under long term note agreements and no outstanding amounts under its revolving credit facility. While we expect to have ongoing access to our credit facility and capital markets, continued access could be adversely affected by current and future economic and business conditions and possible credit rating downgrades. To the extent current market conditions continue for a prolonged period or worsen, we may be forced to reduce or delay capital and operational expenditures, divest assets, seek additional debt or equity financing, or refinance all or a portion of our debt. Workforce Reduction On January 22, 2016 and March 18, 2016, we reduced our workforce as part of an overall plan to reduce costs and better align our workforce with the needs of our business in light of current oil and natural gas commodity prices. In connection with the reductions, we incurred charges of approximately $3.2 million and $0.8 million , respectively, in the first quarter of 2016 for one-time termination benefits which are included in general and administrative expense on the consolidated income statement.

Derivative Commodity Instrument

Derivative Commodity Instruments	3 Months Ended
	Mar. 31, 2016
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. 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) March 31, 2016 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 $ 23,182 $ (4,372 ) $ 18,810 $ — $ — $ 18,810 Noncurrent derivative instruments 115 33 148 — — 148 Total derivative assets 23,297 (4,339 ) 18,958 — — 18,958 Liabilities Derivative instruments 9,840 (4,372 ) 5,468 — — 5,468 Noncurrent derivative instruments 240 33 273 — — 273 Total derivative liabilities 10,080 (4,339 ) 5,741 — — 5,741 Total derivatives $ 13,217 $ — $ 13,217 $ — $ — $ 13,217 (in thousands) December 31, 2015 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 $ 72,563 $ (15,600 ) $ 56,963 $ — $ — $ 56,963 Liabilities Derivative instruments 16,059 (15,600 ) 459 — — 459 Total derivatives $ 56,504 $ — $ 56,504 $ — $ — $ 56,504 *All derivative instruments were current at December 31, 2015. 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 six of our active counterparties and in a net loss position with the remaining four at March 31, 2016 . The largest counterparty net gain positions at March 31, 2016 , Morgan Stanley Capital Group Inc. and BP Corporation North America Inc., constituted approximately $11.3 million and $6.1 million , respectively, of Energen’s total gain on fair value of derivatives. The following table details 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 Gain recognized in income on derivatives Gain (loss) on derivative instruments, net $ 5,455 $ 34,036 As of March 31, 2016, Energen had entered into the following transactions for the remainder of 2016 and subsequent years: Production Period Total Hedged Volumes Average Contract Price Description Oil 2016 5,495 MBbl $44.78 Bbl NYMEX Swaps 2017 1,080 MBbl $45.05 Bbl NYMEX Swaps Oil Basis Differential 2016 5,643 MBbl $(1.92) Bbl WTI/WTI Basis Swaps 2016 1,572 MBbl $(1.64) Bbl WTS/WTI Basis Swaps Natural Gas 2016 5.4 Bcf $2.30 Mcf Basin Specific Swaps - Permian WTI - West Texas Intermediate/Midland, WTI - West Texas Intermediate/Cushing WTS - West Texas Sour/Midland, WTI - West Texas Intermediate/Cushing As of March 31, 2016 , the maximum term over which Energen has hedged exposures to the variability of cash flows is through December 31, 2017.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2016
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 ended March 31, 2016 . 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: March 31, 2016 (in thousands) Level 2 Level 3 Total Assets: Derivative instruments $ 21,585 $ (2,775 ) $ 18,810 Noncurrent derivative instruments 148 — 148 Total assets 21,733 (2,775 ) 18,958 Liabilities: Derivative instruments (89 ) (5,379 ) (5,468 ) Noncurrent derivative instruments (273 ) — (273 ) Total liabilities (362 ) (5,379 ) (5,741 ) Net derivative asset (liability) $ 21,371 $ (8,154 ) $ 13,217 December 31, 2015 (in thousands) Level 2 Level 3 Total Assets: Derivative instruments $ 69,864 $ (12,901 ) $ 56,963 Liabilities: Derivative instruments 2,699 (3,158 ) (459 ) Net derivative asset (liability) $ 72,563 $ (16,059 ) $ 56,504 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 March 31, 2016, Energen had interest rate swap agreements with a notional value of $50.0 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 $0.1 million and a $0.2 million liability at March 31, 2016 and December 31, 2015 , respectively, and is 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 $0.8 million change in the fair value of open Level 3 derivative contracts and to the results of operations. The table below sets forth a summary of changes in the fair value of Energen’s Level 3 derivative commodity instruments as follows: Three months ended March 31, (in thousands) 2016 2015 Balance at beginning of period $ (16,059 ) $ 24,436 Realized gains (losses) (5,518 ) 13,153 Unrealized gains (losses) relating to instruments held at the reporting date* 7,905 (22,023 ) Settlements during period 5,518 (13,153 ) Balance at end of period $ (8,154 ) $ 2,413 *Includes $2.2 million in mark-to-market gains and $10.3 million in mark-to-market losses for the three months ended March 31, 2016 and 2015, 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 March 31, 2016 Valuation Technique* Unobservable Input* Range Oil Basis - WTI/WTI 2016 $ (8,153 ) Discounted Cash Flow Forward Basis ($0.20 - $0.43) Bbl Oil Basis - WTS/WTI 2016 $ (1,443 ) Discounted Cash Flow Forward Basis ($0.49 - $0.69) Bbl Natural Gas Basis - Permian 2016 $ 1,442 Discounted Cash Flow Forward Basis ($0.17 - $0.18) 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. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Certain assets and liabilities are reported at fair value on a nonrecurring basis in Energen’s consolidated balance sheets. The following methods and assumptions were used to estimate the fair values. 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. See Note 11, Asset Retirement Obligations, for further discussion related to these ARO’s. These assumptions are classified as Level 3 fair value. Asset Impairments: We monitor our oil and natural gas properties as well as the market and business environments in which we operate and make assessments about events that could result in potential impairment. Such potential events may include, but are not limited to, commodity price declines, unanticipated increased operating costs, and lower than expected field production performance. If a material event occurs, Energen makes an estimate of undiscounted future cash flows to determine whether the asset is impaired. If the asset is impaired, we will record an impairment loss for the difference between the net book value of the properties and the fair value of the properties. The fair value of the properties typically is estimated using discounted cash flows and values derived from purchase and sale agreements and similar support as applicable. Cash flow and fair value estimates require Energen to make projections and assumptions for pricing, demand, competition, operating costs, legal and regulatory issues, discount rates and other factors for many years into the future. These assumptions are classified as Level 3 fair value. See Note 13, Asset Impairment, for impairments recognized by Energen during the three months ended March 31, 2016 and 2015. 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 Company invested in certain short-term investments that qualify and were classified as cash and cash equivalents. Energen had allowance for doubtful accounts of $0.7 million at both March 31, 2016 and December 31, 2015, respectively. The fair value of Energen’s long-term debt, including the current portion, was approximately $481.2 million and $690.1 million and had a carrying value of $554.0 million and $776.5 million at March 31, 2016 and December 31, 2015 , 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.

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Long-Term Debt	LONG-TERM DEBT Long-term debt consisted of the following: (in thousands) March 31, 2016 December 31, 2015 Credit facility $ — $ 222,500 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 Total 554,000 776,500 Less unamortized debt discount 407 413 Less unamortized debt issuance costs 2,446 2,537 Total $ 551,147 $ 773,550 The aggregate maturities of Energen’s long-term debt outstanding at March 31, 2016 are as follows: (in thousands) Remaining 2016 2017 2018 2019 2020 2021 and thereafter $— $19,000 $— $— $— $535,000 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 five -year syndicated secured credit facility with domestic and foreign lenders. On April 13, 2016, the borrowing base and aggregate commitments were reduced to $1.05 billion in association with the semi-annual redetermination required under the agreement. Energen’s obligations under the syndicated credit facility are unconditionally guaranteed by Energen Resources. Subject to release of collateral in certain periods upon the achievement of certain investment grade ratings from designated ratings agencies, the credit facility is collateralized by certain assets of Energen, including a pledge of equity interests in subsidiaries of Energen other than Energen Resources, and by mortgages on substantially all of Energen Resources’ oil and natural gas properties. 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. In addition, the terms of our credit facility limit the amount we can borrow to a borrowing base amount which is determined by our lenders in their sole discretion based on their valuation of our proved reserves and their internal criteria including commodity price outlook. The borrowing base amount is subject to redetermination semi-annually and for event-driven unscheduled redeterminations. Our next scheduled redetermination is October 1, 2016. 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 March 31, 2016 . The following is a summary of information relating to Energen’s credit facility: (in thousands) March 31, 2016 December 31, 2015 Credit facility outstanding $ — $ 222,500 Available for borrowings 1,400,000 1,177,500 Total borrowing commitments* $ 1,400,000 $ 1,400,000 *Effective April 13, 2016, borrowing commitments were lowered to $1.05 billion . (in thousands) March 31, 2016 December 31, 2015 Maximum amount outstanding at any month-end $ 214,500 $ 685,000 Average daily amount outstanding $ 134,934 $ 358,929 Weighted average interest rates based on: Average daily amount outstanding 1.72 % 1.60 % Amount outstanding at period-end — % 1.64 % Energen’s interest expense was $9.8 million and $11.8 million for the three months ended March 31, 2016 and 2015, respectively. Energen’s total interest expense for the three months ended March 31, 2016 and 2015 included debt issuance costs related to long-term debt, including our credit facility, of $0.8 million and $0.8 million , respectively. Energen had no capitalized interest for the three months ended March 31, 2016. Capitalized interest for the three months ended March 31, 2015 was not significant. At March 31, 2016, Energen paid commitment fees on the unused portion of the available credit facility at a current annual rate of 30 basis points.

Reconciliation of Earnings Per

Reconciliation of Earnings Per Share (EPS)	3 Months Ended
	Mar. 31, 2016
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) March 31, 2016 March 31, 2015 Net Per Share Net Per Share Loss Shares Amount Loss Shares Amount Basic EPS $ (203,116 ) 86,632 $ (2.34 ) $ (15,420 ) 72,830 $ (0.21 ) Effect of dilutive securities Stock options — — Non-vested restricted stock — — Performance share awards — — Diluted EPS $ (203,116 ) 86,632 $ (2.34 ) $ (15,420 ) 72,830 $ (0.21 ) In periods of loss, shares that otherwise would have been included in diluted average common shares outstanding are excluded. The Company had 233,547 and 284,150 of excluded shares for the three months ended March 31, 2016 and 2015, respectively. Energen had the following shares that were excluded from the computation of diluted EPS, as inclusion would be anti-dilutive: Three months ended (in thousands) 2016 2015 Stock options 709 — Performance share awards 114 —

Equity Offering

Equity Offering	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Equity Offering	EQUITY OFFERING During the first quarter of 2016, Energen issued 18,170,000 additional shares of common stock through a public equity offering. We received net proceeds of approximately $381.1 million , after deducting offering expenses. Net proceeds from this offering were used to repay borrowings under our credit facility and for general corporate purposes. During the second quarter of 2015, Energen issued 5,700,000 additional shares of common stock through a public equity offering. We received net proceeds of approximately $398.6 million , after deducting offering expenses. Net proceeds from this offering were used to repay borrowings under our credit facility and for general corporate purposes.

Stock Compensation

Stock Compensation	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [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. Restricted Stock: Additionally, the Stock Incentive Plan provides for the grant of restricted stock and restricted stock units. In March 2016, Energen awarded 154,633 restricted stock units with a grant-date fair value of $26.77 . These awards have a three year vesting period and 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 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 136,191 performance share awards during the first quarter of 2016 with a three year vesting period and a grant-date fair value of $22.74 . Stock Repurchase Program During the three months ended March 31, 2016 and 2015, Energen had non-cash purchases of approximately $2.4 million and $4.4 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	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS 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 (in thousands) 2016 2015 Components of net periodic benefit cost: Interest cost $ — $ 204 Actuarial loss — 184 Settlement charge 3,325 2,662 Net periodic expense $ 3,325 $ 3,050 Energen’s non-qualified supplemental retirement plans were terminated effective December 31, 2014. Distributions under the plans were partially made in the first quarter of 2015 with the remainder of approximately $14.5 million paid in the first quarter of 2016. The Company expects to make no additional benefit payments with respect to the termination of the non-qualified supplemental retirement plans. In the first quarter of 2016 and 2015, Energen incurred a settlement charge of $3.3 million and $2.5 million , respectively, for the payment of lump sums from the non-qualified supplemental retirement plans. Also in the first quarter of 2015, Energen incurred settlement charges of $0.2 million for the payment of lump sums from the qualified defined benefit pension plans. The components of net periodic postretirement benefit expense for Energen’s postretirement benefit plan were as follows: Three months ended (in thousands) 2016 2015 Components of net periodic benefit cost: Service cost $ 23 $ 98 Interest cost 66 117 Expected long-term return on assets (111 ) (114 ) Prior service cost amortization (125 ) — Settlement charge 45 — Curtailment gain (816 ) — Net periodic (income) expense $ (918 ) $ 101 There are no required contributions to the postretirement benefit plan during 2016. In the three months ended March 31, 2016, Energen incurred a curtailment gain of $0.8 million in connection with the reduction in workforce.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
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 5.3 million barrels of oil equivalent (MMBOE) through October 2020 . 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, including an estimate of legal costs to be incurred, 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. On November 4, 2015, Energen Resources filed a quiet title action against Endeavor Energy Resources. L.P. in the District Court of Howard County, Texas, to remove a cloud on the title to approximately 10,000 acres leased by Energen Resources in that county. Energen Resources believes the cloud on title arises from a prior, unreleased but partially terminated oil and gas lease covering the leased lands. Endeavor filed a counterclaim alleging Energen Resources tortiously interfered with a prospective contract seeking $300 million in damages. On April 28, 2016, the trial judge ruled with respect to the acreage not held by production that Endeavor’s lease terminated prior to the date Energen Resources entered into its lease and additionally ruled that Endeavor’s claim for tortuous interference will be dismissed with prejudice. 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. 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 and Energen Resources appealed the Revised Order. In the Revised Order, ONRR ordered that Energen pay additional royalties on production from certain federal leases in the amount of $129,700 . At ONRR’s request the Revised Order was also remanded in August 2015. On April 15, 2016 ONRR issued its Second Revised Order. The Second Revised Order directs Energen Resources to pay additional royalties of $189,000 , replacing the previous demand of $129,700 . Energen had previously estimated that application of the ONRR position to all of the Company’s federal leases would result in ONRR claims up to approximately $24 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 plans to appeal and vigorously contest the Second Revised Order, the predecessor orders 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 March 31, 2016 .

Exploratory Costs

Exploratory Costs	3 Months Ended
	Mar. 31, 2016
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 proved properties in the balance sheets. If the exploratory well is determined to be a dry hole, the 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 (in thousands) 2016 2015 Capitalized exploratory well costs at beginning of period $ 103,588 $ 119,439 Additions pending determination of proved reserves 83,446 230,061 Reclassifications due to determination of proved reserves (81,443 ) (234,291 ) Capitalized exploratory well costs at end of period $ 105,591 $ 115,209 The following table sets forth capitalized exploratory well costs: (in thousands) March 31, 2016 December 31, 2015 Exploratory wells in progress (drilling rig not released) $ 2,164 $ 1,760 Capitalized exploratory well costs capitalized for a period of one year or less 99,768 101,828 Capitalized exploratory well cost for a period greater than one year 3,659 — Total capitalized exploratory well costs $ 105,591 $ 103,588 At March 31, 2016 , Energen had 33 gross exploratory wells either drilling or waiting on results from completion and testing in the Permian Basin. As of March 31, 2016, the Company had one gross well capitalized greater than a year. This well is scheduled for completion during 2017. No wells were capitalized for a period greater than one year as of December 31, 2015.

Asset Retirement Obligations

Asset Retirement Obligations	3 Months Ended
	Mar. 31, 2016
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: (in thousands) Balance as of December 31, 2015 $ 89,990 Liabilities incurred 40 Liabilities settled (249 ) Accretion expense 1,757 Reclassification associated with held for sale properties* (1,315 ) Balance as of March 31, 2016 $ 90,223 *Adjustment to the reclassification of the asset retirement obligation associated with certain properties included as liabilities related to assets held for sale in current liabilities on the balance sheet at March 31, 2016.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2016
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) Balance as of December 31, 2015 $ 263 Other comprehensive income (loss) before reclassifications (9 ) Amounts reclassified from accumulated other comprehensive income (loss) 1,812 Change in accumulated other comprehensive income (loss) 1,803 Balance as of March 31, 2016 $ 2,066 The following table provides details of the reclassifications out of accumulated other comprehensive income (loss). Three months ended March 31, 2016 2015 (in thousands) Amounts Reclassified Line Item Where Presented Pension and postretirement plans: Prior service cost $ 125 $ — General and administrative Actuarial losses (3,058 ) (2,847 ) General and administrative Total pension and postretirement plans (2,933 ) (2,847 ) Income tax expense 1,121 996 Net of tax (1,812 ) (1,851 ) Total reclassifications for the period $ (1,812 ) $ (1,851 )

Asset Impairment

Asset Impairment	3 Months Ended
	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Asset Impairment	ASSET IMPAIRMENT Impairments recognized by Energen are presented below: Three months ended (in thousands) 2016 2015 Permian Basin oil properties Central Basin Platform $ 187,043 $ — Delaware Basin 21,288 4,330 San Juan Basin properties 7,519 — Permian Basin unproved leasehold properties 4,135 2,005 San Juan Basin unproved leasehold properties 40 248 Total asset impairments $ 220,025 $ 6,583 Non-cash impairment writedowns are reflected in asset impairment on the consolidated income statement. Permian Basin: During the first quarter of 2016, Energen recognized non-cash impairment writedowns in the Permian Basin of $208.3 million to adjust the carrying amount of these properties to their fair value. We estimate future discounted cash flows in determining fair value using commodity assumptions, which are based on the commodity price curve for five years and then escalated at 3 percent through our assumed price cap. Our commodity price assumptions declined over the first quarter by approximately 5 percent for oil and 4 percent for natural gas in comparable periods. During the first quarter of 2015, Energen recognized a non-cash impairment writedown of $4.3 million . In the first quarter of 2016, Energen recognized unproved leasehold writedowns of $4.1 million primarily on Permian Basin oil properties in the Delaware Basin and the Central Basin Platform. Energen recognized unproved leasehold writedowns primarily on Permian Basin oil properties in the Central Basin Platform of $2.0 million during the first quarter of 2015. San Juan Basin: During the first quarter of 2016, Energen recognized non-cash impairment writedowns on held for sale properties in the San Juan Basin of $7.5 million to adjust the carrying amount of these properties to their fair value. During the first quarter of 2016, Energen recognized an insignificant amount of unproved leasehold writedowns on San Juan Basin properties. Energen recognized unproved leasehold writedowns on San Juan Basin properties of $0.2 million during the first quarter of 2015.

Acquisition and Disposition of

Acquisition and Disposition of Properties	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Acquisition and Disposition of Properties	ACQUISITION AND DISPOSITION OF PROPERTIES The following table details held for sale properties by major classes of assets and liabilities. These property sales do not qualify for discontinued operations: (in thousands) March 31, 2016 Permian Basin San Juan Basin Total Oil and natural gas properties $ 260,253 $ 311,282 $ 571,535 Less accumulated depreciation, depletion and amortization (166,254 ) (222,047 ) (388,301 ) Total assets held for sale 93,999 89,235 183,234 Other long-term liabilities (1,086 ) (13,016 ) (14,102 ) Total liabilities held for sale (1,086 ) (13,016 ) (14,102 ) Total net assets held for sale $ 92,913 $ 76,219 $ 169,132 (in thousands) December 31, 2015 San Juan Basin Inventories $ 3,651 Oil and natural gas properties 305,386 Less accumulated depreciation, depletion and amortization (219,059 ) Other property and equipment, net 3,761 Total assets held for sale 93,739 Other long-term liabilities (12,789 ) Total liabilities held for sale (12,789 ) Total net assets held for sale $ 80,950 On March 31, 2015, Energen completed the sale of the majority of its natural gas assets in the San Juan Basin in New Mexico and Colorado (effective as of January 1, 2015) for an aggregate purchase price of $395 million . The sales proceeds were reduced by purchase price adjustments of approximately $11 million related to the operations of the San Juan Basin properties subsequent to December 31, 2014 and one-time adjustments related primarily to liabilities assumed by the buyer, which resulted in pre-tax proceeds to Energen of approximately $384 million before consideration of transaction costs of approximately $2.8 million . Energen recognized a pre-tax gain of $27.0 million on the sale. Energen used proceeds from the sale to reduce long-term indebtedness. At December 31, 2014, proved reserves associated with these San Juan Basin properties totaled 69,038 MBOE. Energen completed an estimated $7.6 million in various purchases of unproved leasehold largely in the Permian Basin during the first quarter of 2016. During 2015, Energen completed an estimated total of $85.7 million in various purchases of unproved leasehold largely in the Permian Basin.

Recently Issued Accounting Stan

Recently Issued Accounting Standards	3 Months Ended
	Mar. 31, 2016
Accounting Changes and Error Corrections [Abstract]
Recently Issued Accounting Standards	RECENTLY ISSUED ACCOUNTING STANDARDS In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2016-09, Improvements to Employee Share-Based Payment Accounting, which makes a number of changes meant to simplify and improve accounting for share-based payments. The amendment is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Energen does not expect the adoption of this ASU to have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases. This update increases transparency and comparability by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The amendment is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Energen does not expect the adoption of this ASU to have a material impact on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. This update requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendment is effective for fiscal years beginning on or after December 15, 2015, and interim periods within those fiscal years. In August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements. This update clarifies the guidance regarding line-of-credit arrangements with regards to the ASU No. 2015-03. ASU 2015-15 allows entities to defer and present debt issue costs as an asset and subsequently amortize the deferred debt issue costs ratably over the term of the line-of-credit arrangement. The adoption of ASU No. 2015-03 did not have a material impact on the consolidated financial statements of Energen. The additional disclosures are included in Note 4, Long-Term Debt. In August 2014, the FASB issued ASU No, 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. This update codifies management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for interim and annual periods ending after December 15, 2016 and early adoption is permitted. The amendments in this ASU will not impact the Company's financial position or results of operations. The new guidance will require a formal assessment of going concern by management based on criteria prescribed in the new guidance. The Company is reviewing its policies and processes to ensure compliance with this new guidance. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. This update is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. It also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. Companies may apply this update retrospectively or using a modified retrospective approach to adjust retained earnings. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers, which deferred the effective date of ASU No. 2014-09 to annual periods beginning after December 15, 2017, including interim reporting periods within that reporting period. We are currently evaluating the impact of this guidance on our financial statements.

Recently Issued Accounting St24

Recently Issued Accounting Standards (Policies)	3 Months Ended
	Mar. 31, 2016
Accounting Changes and Error Corrections [Abstract]
Recently Issued Accounting Standards	In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2016-09, Improvements to Employee Share-Based Payment Accounting, which makes a number of changes meant to simplify and improve accounting for share-based payments. The amendment is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Energen does not expect the adoption of this ASU to have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases. This update increases transparency and comparability by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The amendment is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Energen does not expect the adoption of this ASU to have a material impact on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. This update requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendment is effective for fiscal years beginning on or after December 15, 2015, and interim periods within those fiscal years. In August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements. This update clarifies the guidance regarding line-of-credit arrangements with regards to the ASU No. 2015-03. ASU 2015-15 allows entities to defer and present debt issue costs as an asset and subsequently amortize the deferred debt issue costs ratably over the term of the line-of-credit arrangement. The adoption of ASU No. 2015-03 did not have a material impact on the consolidated financial statements of Energen. The additional disclosures are included in Note 4, Long-Term Debt. In August 2014, the FASB issued ASU No, 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. This update codifies management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for interim and annual periods ending after December 15, 2016 and early adoption is permitted. The amendments in this ASU will not impact the Company's financial position or results of operations. The new guidance will require a formal assessment of going concern by management based on criteria prescribed in the new guidance. The Company is reviewing its policies and processes to ensure compliance with this new guidance. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. This update is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. It also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. Companies may apply this update retrospectively or using a modified retrospective approach to adjust retained earnings. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers, which deferred the effective date of ASU No. 2014-09 to annual periods beginning after December 15, 2017, including interim reporting periods within that reporting period. We are currently evaluating the impact of this guidance on our financial statements.

Derivative Commodity Instrume25

Derivative Commodity Instruments (Tables)	3 Months Ended
	Mar. 31, 2016
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) March 31, 2016 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 $ 23,182 $ (4,372 ) $ 18,810 $ — $ — $ 18,810 Noncurrent derivative instruments 115 33 148 — — 148 Total derivative assets 23,297 (4,339 ) 18,958 — — 18,958 Liabilities Derivative instruments 9,840 (4,372 ) 5,468 — — 5,468 Noncurrent derivative instruments 240 33 273 — — 273 Total derivative liabilities 10,080 (4,339 ) 5,741 — — 5,741 Total derivatives $ 13,217 $ — $ 13,217 $ — $ — $ 13,217 (in thousands) December 31, 2015 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 $ 72,563 $ (15,600 ) $ 56,963 $ — $ — $ 56,963 Liabilities Derivative instruments 16,059 (15,600 ) 459 — — 459 Total derivatives $ 56,504 $ — $ 56,504 $ — $ — $ 56,504 *All derivative instruments were current at December 31, 2015.
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following table details 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 Gain recognized in income on derivatives Gain (loss) on derivative instruments, net $ 5,455 $ 34,036
Schedule of Hedging Transactions	As of March 31, 2016, Energen had entered into the following transactions for the remainder of 2016 and subsequent years: Production Period Total Hedged Volumes Average Contract Price Description Oil 2016 5,495 MBbl $44.78 Bbl NYMEX Swaps 2017 1,080 MBbl $45.05 Bbl NYMEX Swaps Oil Basis Differential 2016 5,643 MBbl $(1.92) Bbl WTI/WTI Basis Swaps 2016 1,572 MBbl $(1.64) Bbl WTS/WTI Basis Swaps Natural Gas 2016 5.4 Bcf $2.30 Mcf Basin Specific Swaps - Permian WTI - West Texas Intermediate/Midland, WTI - West Texas Intermediate/Cushing WTS - West Texas Sour/Midland, WTI - West Texas Intermediate/Cushing

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2016
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: March 31, 2016 (in thousands) Level 2 Level 3 Total Assets: Derivative instruments $ 21,585 $ (2,775 ) $ 18,810 Noncurrent derivative instruments 148 — 148 Total assets 21,733 (2,775 ) 18,958 Liabilities: Derivative instruments (89 ) (5,379 ) (5,468 ) Noncurrent derivative instruments (273 ) — (273 ) Total liabilities (362 ) (5,379 ) (5,741 ) Net derivative asset (liability) $ 21,371 $ (8,154 ) $ 13,217 December 31, 2015 (in thousands) Level 2 Level 3 Total Assets: Derivative instruments $ 69,864 $ (12,901 ) $ 56,963 Liabilities: Derivative instruments 2,699 (3,158 ) (459 ) Net derivative asset (liability) $ 72,563 $ (16,059 ) $ 56,504
Schedule of Changes in Fair Value of Derivative Instruments Classified as Level 3	The table below sets forth a summary of changes in the fair value of Energen’s Level 3 derivative commodity instruments as follows: Three months ended March 31, (in thousands) 2016 2015 Balance at beginning of period $ (16,059 ) $ 24,436 Realized gains (losses) (5,518 ) 13,153 Unrealized gains (losses) relating to instruments held at the reporting date* 7,905 (22,023 ) Settlements during period 5,518 (13,153 ) Balance at end of period $ (8,154 ) $ 2,413 *Includes $2.2 million in mark-to-market gains and $10.3 million in mark-to-market losses for the three months ended March 31, 2016 and 2015, 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 March 31, 2016 Valuation Technique* Unobservable Input* Range Oil Basis - WTI/WTI 2016 $ (8,153 ) Discounted Cash Flow Forward Basis ($0.20 - $0.43) Bbl Oil Basis - WTS/WTI 2016 $ (1,443 ) Discounted Cash Flow Forward Basis ($0.49 - $0.69) Bbl Natural Gas Basis - Permian 2016 $ 1,442 Discounted Cash Flow Forward Basis ($0.17 - $0.18) 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.

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	Long-term debt consisted of the following: (in thousands) March 31, 2016 December 31, 2015 Credit facility $ — $ 222,500 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 Total 554,000 776,500 Less unamortized debt discount 407 413 Less unamortized debt issuance costs 2,446 2,537 Total $ 551,147 $ 773,550
Maturities of Long-term Debt	The aggregate maturities of Energen’s long-term debt outstanding at March 31, 2016 are as follows: (in thousands) Remaining 2016 2017 2018 2019 2020 2021 and thereafter $— $19,000 $— $— $— $535,000
Summary of Credit Facilities	The following is a summary of information relating to Energen’s credit facility: (in thousands) March 31, 2016 December 31, 2015 Credit facility outstanding $ — $ 222,500 Available for borrowings 1,400,000 1,177,500 Total borrowing commitments* $ 1,400,000 $ 1,400,000 *Effective April 13, 2016, borrowing commitments were lowered to $1.05 billion . (in thousands) March 31, 2016 December 31, 2015 Maximum amount outstanding at any month-end $ 214,500 $ 685,000 Average daily amount outstanding $ 134,934 $ 358,929 Weighted average interest rates based on: Average daily amount outstanding 1.72 % 1.60 % Amount outstanding at period-end — % 1.64 %

Reconciliation of Earnings Pe28

Reconciliation of Earnings Per Share (EPS) (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Reconciliation	Three months ended Three months ended (in thousands, except per share amounts) March 31, 2016 March 31, 2015 Net Per Share Net Per Share Loss Shares Amount Loss Shares Amount Basic EPS $ (203,116 ) 86,632 $ (2.34 ) $ (15,420 ) 72,830 $ (0.21 ) Effect of dilutive securities Stock options — — Non-vested restricted stock — — Performance share awards — — Diluted EPS $ (203,116 ) 86,632 $ (2.34 ) $ (15,420 ) 72,830 $ (0.21 )
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 (in thousands) 2016 2015 Stock options 709 — Performance share awards 114 —

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2016
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 (in thousands) 2016 2015 Components of net periodic benefit cost: Interest cost $ — $ 204 Actuarial loss — 184 Settlement charge 3,325 2,662 Net periodic expense $ 3,325 $ 3,050
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 (in thousands) 2016 2015 Components of net periodic benefit cost: Service cost $ 23 $ 98 Interest cost 66 117 Expected long-term return on assets (111 ) (114 ) Prior service cost amortization (125 ) — Settlement charge 45 — Curtailment gain (816 ) — Net periodic (income) expense $ (918 ) $ 101

Exploratory Costs (Tables)

Exploratory Costs (Tables)	3 Months Ended
	Mar. 31, 2016
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 (in thousands) 2016 2015 Capitalized exploratory well costs at beginning of period $ 103,588 $ 119,439 Additions pending determination of proved reserves 83,446 230,061 Reclassifications due to determination of proved reserves (81,443 ) (234,291 ) Capitalized exploratory well costs at end of period $ 105,591 $ 115,209 The following table sets forth capitalized exploratory well costs: (in thousands) March 31, 2016 December 31, 2015 Exploratory wells in progress (drilling rig not released) $ 2,164 $ 1,760 Capitalized exploratory well costs capitalized for a period of one year or less 99,768 101,828 Capitalized exploratory well cost for a period greater than one year 3,659 — Total capitalized exploratory well costs $ 105,591 $ 103,588

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	3 Months Ended
	Mar. 31, 2016
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: (in thousands) Balance as of December 31, 2015 $ 89,990 Liabilities incurred 40 Liabilities settled (249 ) Accretion expense 1,757 Reclassification associated with held for sale properties* (1,315 ) Balance as of March 31, 2016 $ 90,223 *Adjustment to the reclassification of the asset retirement obligation associated with certain properties included as liabilities related to assets held for sale in current liabilities on the balance sheet at March 31, 2016.

Accumulated Other Comprehensi32

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2016
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) Balance as of December 31, 2015 $ 263 Other comprehensive income (loss) before reclassifications (9 ) Amounts reclassified from accumulated other comprehensive income (loss) 1,812 Change in accumulated other comprehensive income (loss) 1,803 Balance as of March 31, 2016 $ 2,066
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 March 31, 2016 2015 (in thousands) Amounts Reclassified Line Item Where Presented Pension and postretirement plans: Prior service cost $ 125 $ — General and administrative Actuarial losses (3,058 ) (2,847 ) General and administrative Total pension and postretirement plans (2,933 ) (2,847 ) Income tax expense 1,121 996 Net of tax (1,812 ) (1,851 ) Total reclassifications for the period $ (1,812 ) $ (1,851 )

Asset Impairment (Tables)

Asset Impairment (Tables)	3 Months Ended
	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Details of Impairment of Long-Lived Assets Held and Used by Asset	Impairments recognized by Energen are presented below: Three months ended (in thousands) 2016 2015 Permian Basin oil properties Central Basin Platform $ 187,043 $ — Delaware Basin 21,288 4,330 San Juan Basin properties 7,519 — Permian Basin unproved leasehold properties 4,135 2,005 San Juan Basin unproved leasehold properties 40 248 Total asset impairments $ 220,025 $ 6,583

Acquisition and Disposition o34

Acquisition and Disposition of Properties (Tables)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Schedule of Assets and Liabilities Held-for-sale	The following table details held for sale properties by major classes of assets and liabilities. These property sales do not qualify for discontinued operations: (in thousands) March 31, 2016 Permian Basin San Juan Basin Total Oil and natural gas properties $ 260,253 $ 311,282 $ 571,535 Less accumulated depreciation, depletion and amortization (166,254 ) (222,047 ) (388,301 ) Total assets held for sale 93,999 89,235 183,234 Other long-term liabilities (1,086 ) (13,016 ) (14,102 ) Total liabilities held for sale (1,086 ) (13,016 ) (14,102 ) Total net assets held for sale $ 92,913 $ 76,219 $ 169,132 (in thousands) December 31, 2015 San Juan Basin Inventories $ 3,651 Oil and natural gas properties 305,386 Less accumulated depreciation, depletion and amortization (219,059 ) Other property and equipment, net 3,761 Total assets held for sale 93,739 Other long-term liabilities (12,789 ) Total liabilities held for sale (12,789 ) Total net assets held for sale $ 80,950

Organization and Basis of Pre35

Organization and Basis of Presentation - Additional Information (Details) - USD ($)	Mar. 18, 2016	Jan. 22, 2016	Mar. 31, 2016	Jun. 30, 2015	Apr. 13, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash			$ 35,806,000			$ 1,272,000
Available for borrowings			1,400,000,000			1,177,500,000
Line of credit, current borrowing capacity			1,400,000,000			1,400,000,000
Proceeds from issuance of common stock net of offering expenses			381,137,000	$ 398,600,000
Gross amount			$ 554,000,000			776,500,000
One-time Termination Benefits
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring charges incurred as a result of workforce reduction	$ 800,000	$ 3,200,000
Common Stock
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Shares issued through public equity offering			18,170,000	5,700,000
Long-term note agreements
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross amount			$ 554,000,000
Credit facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross amount			$ 0			$ 222,500,000
Subsequent Event | Credit facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Line of credit, current borrowing capacity					$ 1,050,000,000

Derivative Commodity Instrume36

Derivative Commodity Instruments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative [Line Items]
Gain on fair value of derivatives	$ 5,455	$ 34,036
Commodity contracts | Morgan Stanley Capital Group Inc
Derivative [Line Items]
Gain on fair value of derivatives	11,300
Commodity contracts | BP Corporation North America, Inc
Derivative [Line Items]
Gain on fair value of derivatives	$ 6,100

Derivative Commodity Instrume37

Derivative Commodity Instruments - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets
Gross Amounts Recognized at Fair Value	$ 23,297
Gross Amounts Offset in the Balance Sheets	(4,339)
Total assets	18,958
Financial Instruments	0
Cash Collateral Received	0
Net Fair Value Presented in the Balance Sheets	18,958
Liabilities
Gross Amounts Recognized at Fair Value	10,080
Gross Amounts Offset in the Balance Sheets	(4,339)
Net Amount Presented in the Balance Sheets	5,741
Financial Instruments	0
Cash Collateral Received	0
Net Fair Value Presented in the Balance Sheets	5,741
Total Derivatives	13,217	$ 56,504
Current Assets
Assets
Gross Amounts Recognized at Fair Value	23,182	72,563
Gross Amounts Offset in the Balance Sheets	(4,372)	(15,600)
Total assets	18,810	56,963
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	18,810	56,963
Noncurrent Assets
Assets
Gross Amounts Recognized at Fair Value	115
Gross Amounts Offset in the Balance Sheets	33
Total assets	148
Financial Instruments	0
Cash Collateral Received	0
Net Fair Value Presented in the Balance Sheets	148
Current Liabilities
Liabilities
Gross Amounts Recognized at Fair Value	9,840	16,059
Gross Amounts Offset in the Balance Sheets	(4,372)	(15,600)
Net Amount Presented in the Balance Sheets	5,468	459
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Fair Value Presented in the Balance Sheets	5,468	$ 459
Noncurrent Liabilities
Liabilities
Gross Amounts Recognized at Fair Value	240
Gross Amounts Offset in the Balance Sheets	33
Net Amount Presented in the Balance Sheets	273
Financial Instruments	0
Cash Collateral Received	0
Net Fair Value Presented in the Balance Sheets	$ 273

Derivative Commodity Instrume38

Derivative Commodity Instruments - Not Designated as Hedging Instruments on the Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Gain (loss) on derivative instruments, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in income on derivatives	$ 5,455	$ 34,036

Derivative Commodity - Reclassi

Derivative Commodity - Reclassification (Details)	3 Months Ended
	Mar. 31, 2016MBblsMcf$ / Mcf$ / bbl
2016 | NYMEX Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	5,495,000
Average Contract Price (dollars per Bbl) | $ / bbl	44.78
2016 | WTI/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	5,643,000
Average Contract Price (dollars per Bbl) | $ / bbl	(1.92)
2016 | WTS/WTI Basis Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	1,572,000
Average Contract Price (dollars per Bbl) | $ / bbl	(1.64)
2016 | Basin Specific Swaps - Permian | Natural Gas
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | Mcf	5,400,000
Average contract price (dollars per Mcf) | $ / Mcf	2.30
2017 | NYMEX Swaps | Crude Oil
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	1,080,000
Average Contract Price (dollars per Bbl) | $ / bbl	45.05

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Noncurrent derivative instruments	$ 148	$ 0
Total assets	18,958
Liabilities:
Total liabilities	(5,741)
Recurring
Assets:
Derivative instruments	18,810	56,963
Noncurrent derivative instruments	148
Total assets	18,958
Liabilities:
Derivative instruments	(5,468)	(459)
Noncurrent derivative instruments	(273)
Total liabilities	(5,741)
Net derivative asset (liability)	13,217	56,504
Recurring | Level 2
Assets:
Derivative instruments	21,585	69,864
Noncurrent derivative instruments	148
Total assets	21,733
Liabilities:
Derivative instruments	(89)	2,699
Noncurrent derivative instruments	(273)
Total liabilities	(362)
Net derivative asset (liability)	21,371	72,563
Recurring | Level 3
Assets:
Derivative instruments	(2,775)	(12,901)
Noncurrent derivative instruments	0
Total assets	(2,775)
Liabilities:
Derivative instruments	(5,379)	(3,158)
Noncurrent derivative instruments	0
Total liabilities	(5,379)
Net derivative asset (liability)	$ (8,154)	$ (16,059)

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes of Derivative Commodity Instruments in Fair Value (Details) - Derivative Commodity Instruments - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ (16,059)	$ 24,436
Realized gains (losses)	(5,518)	13,153
Unrealized gains (losses) relating to instruments held at the reporting date	7,905	(22,023)
Settlements during period	5,518	(13,153)
Balance at end of period	(8,154)	2,413
Mark-to-market gain (loss) included in earnings	$ 2,200	$ (10,300)

Fair Value Measurements - Level

Fair Value Measurements - Level 3 Measurements of Derivative Commodity Instruments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)$ / Mcf$ / bbl
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Derivative liabilities	$ (5,741)
Derivative assets	18,958
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTI/WTI | 2016
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Derivative liabilities	$ (8,153)
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTI/WTI | 2016 | Minimum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per barrel | $ / bbl	(0.20)
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTI/WTI | 2016 | Maximum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per barrel | $ / bbl	(0.43)
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTS/WTI | 2016
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Derivative liabilities	$ (1,443)
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTS/WTI | 2016 | Minimum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per barrel | $ / bbl	(0.49)
Discounted Cash Flow Valuation Technique | Level 3 | Oil Basis - WTS/WTI | 2016 | Maximum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per barrel | $ / bbl	(0.69)
Discounted Cash Flow Valuation Technique | Level 3 | Natural Gas Basis - Permian | 2016
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Derivative assets	$ 1,442
Discounted Cash Flow Valuation Technique | Level 3 | Natural Gas Basis - Permian | 2016 | Minimum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per cubic foot | $ / Mcf	(0.17)
Discounted Cash Flow Valuation Technique | Level 3 | Natural Gas Basis - Permian | 2016 | Maximum
Fair Value Inputs, Derivatives, Quantitative Information [Line Items]
Price per cubic foot | $ / Mcf	(0.18)

Fair Value Measurements - Addi

Fair Value Measurements - Additional Information (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for doubtful accounts	$ 700,000	$ 700,000
Long-term debt carrying value	554,000,000	776,500,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sensitivity analysis of fair value of 10 percent change in commodity prices	800,000
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt fair value	481,200,000	690,100,000
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt carrying value	554,000,000	776,500,000
Credit facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt carrying value	0	222,500,000
Credit facility | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face amount	$ 50,000,000
Interest rate	1.0425%
Credit facility | Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value interest rate swap	$ 100,000	$ 200,000

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Gross amount	$ 554,000	$ 776,500
Less unamortized debt discount	407	413
Less unamortized debt issuance costs	2,446	2,537
Long-term debt	551,147	773,550
Credit facility
Debt Instrument [Line Items]
Gross amount	0	222,500
Medium-term Notes | 7.40% Medium-term Notes, Series A, due July 24, 2017
Debt Instrument [Line Items]
Gross amount	$ 2,000	$ 2,000
Stated interest rate	7.40%	7.40%
Medium-term Notes | 7.36% Medium-term Notes, Series A, due July 24, 2017
Debt Instrument [Line Items]
Gross amount	$ 15,000	$ 15,000
Stated interest rate	7.36%	7.36%
Medium-term Notes | 7.23% Medium-term Notes, Series A, due July 28, 2017
Debt Instrument [Line Items]
Gross amount	$ 2,000	$ 2,000
Stated interest rate	7.23%	7.23%
Medium-term Notes | 7.32% Medium-term Notes, Series A, due July 28, 2022
Debt Instrument [Line Items]
Gross amount	$ 20,000	$ 20,000
Stated interest rate	7.32%	7.32%
Medium-term Notes | 7.60% Medium-term Notes, Series A, due July 26, 2027
Debt Instrument [Line Items]
Gross amount	$ 5,000	$ 5,000
Stated interest rate	7.60%	7.60%
Medium-term Notes | 7.35% Medium-term Notes, Series A, due July 28, 2027
Debt Instrument [Line Items]
Gross amount	$ 10,000	$ 10,000
Stated interest rate	7.35%	7.35%
Medium-term Notes | 7.125% Medium-term Notes, Series B, due February 15, 2028
Debt Instrument [Line Items]
Gross amount	$ 100,000	$ 100,000
Stated interest rate	7.125%	7.125%
Notes Payable | 4.625% Notes, due September 1, 2021
Debt Instrument [Line Items]
Gross amount	$ 400,000	$ 400,000
Stated interest rate	4.625%	4.625%

Long-Term Debt - Maturities of

Long-Term Debt - Maturities of Long-Term Debt (Details) $ in Thousands	Mar. 31, 2016USD ($)
Debt Disclosure [Abstract]
Remaining 2,016	$ 0
2,017	19,000
2,018	0
2,019	0
2,020	0
2021 and thereafter	$ 535,000

Long-Term Debt - Credit Facilit

Long-Term Debt - Credit Facilities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Credit facility outstanding	$ 0	$ 222,500
Available for borrowings	1,400,000	1,177,500
Total borrowing commitments	1,400,000	1,400,000
Maximum amount outstanding at any month-end	214,500	685,000
Average daily amount outstanding	$ 134,934	$ 358,929
Average daily amount outstanding interest rate	1.72%	1.60%
Amount outstanding at period-end interest rate	0.00%	1.64%

Long-Term Debt - Additional In

Long-Term Debt - Additional Information (Details) - USD ($)	Sep. 02, 2014	Mar. 31, 2016	Mar. 31, 2015	Apr. 13, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Cross default provision, threshold amount		$ 10,000,000
Available for borrowings		1,400,000,000			$ 1,177,500,000
Initial borrowing base		$ 1,400,000,000			$ 1,400,000,000
Loan limit percentage (less than)		10.00%
Credit facility cross default provision, threshold amount		$ 75,000,000
Interest expense		9,833,000	$ 11,758,000
Debt issuance costs		800,000	$ 800,000
Capitalized interest expense		$ 0
Commitment fee (basis points)		0.30%
Syndicated Credit Facility | Credit Facility, September 2, 2014
Debt Instrument [Line Items]
Term of credit facility	5 years
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		1.50
Credit facility | Subsequent Event
Debt Instrument [Line Items]
Initial borrowing base				$ 1,050,000,000

Reconciliation of Earnings Pe48

Reconciliation of Earnings Per Share (EPS) - Earnings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Loss, Basic EPS	$ (203,116)	$ (15,420)
Basic Average Common Shares Outstanding (in shares)	86,632	72,830
Earnings Per Share, Basic (in dollars per share)	$ (2.34)	$ (0.21)
Effect of dilutive securities
Net Loss, Diluted EPS	$ (203,116)	$ (15,420)
Diluted Average Common Shares Outstanding (in shares)	86,632	72,830
Earnings Per Share, Diluted (dollars per share)	$ (2.34)	$ (0.21)
Stock options
Effect of dilutive securities
Incremental common shares attributable to share-based payment arrangements	0	0
Non-vested restricted stock
Effect of dilutive securities
Incremental common shares attributable to share-based payment arrangements	0	0
Performance share awards
Effect of dilutive securities
Incremental common shares attributable to share-based payment arrangements	0	0

Reconciliation of Earnings Pe49

Reconciliation of Earnings Per Share (EPS) - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	233,547	284,150
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	709,000	0
Performance share awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	114,000	0

Equity Offering (Details)

Equity Offering (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Jun. 30, 2015
Class of Stock [Line Items]
Proceeds from issuance of common stock net of offering expenses	$ 381,137	$ 398,600
Common Stock
Class of Stock [Line Items]
Shares issued through public equity offering	18,170,000	5,700,000

Stock Compensation (Details)

Stock Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Noncash payments for repurchase of common stock		$ 2.4	$ 4.4
Stock Options | Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period		3 years
Expiration period		10 years
Restricted Stock Units (RSUs) | Stock Incentive Plan | 3 year vesting period
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period	3 years
Grants in period (in shares)	154,633
Weighted average grant date fair value (in dollars per share)	$ 26.77
Performance share awards | Stock Incentive Plan | 3 year vesting period
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period		3 years
Grants in period (in shares)		136,191
Weighted average grant date fair value (in dollars per share)		$ 22.74

Employee Benefit Plans - Compon

Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plans
Components of net periodic benefit cost:
Interest cost	$ 0	$ 204
Actuarial loss	0	184
Settlement charge	3,325	2,662
Net periodic (income) expense	3,325	3,050
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	23	98
Interest cost	66	117
Expected long-term return on assets	(111)	(114)
Prior service cost amortization	(125)	0
Settlement charge	45	0
Curtailment gain	(816)	0
Net periodic (income) expense	$ (918)	$ 101

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by employer	$ 14,500,000
Estimated amount of additional benefit payments	0
Settlement charges	3,300,000	$ 2,500,000
Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Curtailment gain	$ 816,000	0
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement charges		$ 200,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) gal in Thousands, a in Thousands	Nov. 04, 2015USD ($)a	Dec. 31, 2008gal	Mar. 31, 2016MMBoe
Crude Oil and Natural Gas
Long-term Purchase Commitment [Line Items]
Delivery commitments (MMBOE) | MMBoe			5.3
Sylacauga, Talladega County, Alabama
Long-term Purchase Commitment [Line Items]
Gallons of wastewater transported | gal		3
Pending Litigation | Energen vs. Endeavor Energy Resources
Long-term Purchase Commitment [Line Items]
Number of acres with cloud on the title | a	10
Damages sought | $	$ 300,000,000

Commitments and Contingencies55

Commitments and Contingencies - New Mexico Audits (Details) - Unfavorable Regulatory Action - USD ($)	Apr. 15, 2016	Aug. 31, 2014	Dec. 31, 2011
Loss Contingencies [Line Items]
Minimum loss contingency range of loss		$ 129,700
Maximum loss contingency range of possible loss			$ 24,000,000
Subsequent Event
Loss Contingencies [Line Items]
Minimum loss contingency range of loss	$ 189,000

Exploratory Costs (Details)

Exploratory Costs (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016USD ($)well	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)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	$ 103,588	$ 119,439	$ 119,439
Additions pending determination of proved reserves	83,446	230,061
Reclassifications due to determination of proved reserves	(81,443)	(234,291)
Capitalized exploratory well costs at end of period	105,591	$ 115,209	103,588
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Exploratory wells in progress (drilling rig not released)	2,164		1,760
Capitalized exploratory well costs capitalized for a period of one year or less	99,768		101,828
Capitalized exploratory well cost for a period greater than one year	3,659		0
Total capitalized exploratory well costs	$ 105,591		$ 103,588
Number of wells in process of drilling | well	33
Number of wells capitalized | well	1		0

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance as of December 31, 2015	$ 89,990
Liabilities incurred	40
Liabilities settled	(249)
Accretion expense	1,757	$ 2,010
Reclassification associated with held for sale properties	(1,315)
Balance as of March 31, 2016	$ 90,223

Accumulated Other Comprehensi58

Accumulated Other Comprehensive Income (Loss) - Rollforward of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Amortization of net loss, including settlement charges, net of tax of $1,168 and $996, respectively	$ 1,890	$ 1,851
Pension and Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2015	263
Other comprehensive income (loss) before reclassifications	(9)
Amortization of net loss, including settlement charges, net of tax of $1,168 and $996, respectively	1,812
Change in accumulated other comprehensive income (loss)	1,803
Balance as of March 31, 2016	$ 2,066

Accumulated Other Comprehensi59

Accumulated Other Comprehensive Income (Loss) - Reclassifications of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	$ (1,812)	$ (1,851)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	125	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	(3,058)	(2,847)
Pension and Postretirement Plans
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	(2,933)	(2,847)
Income tax expense	1,121	996
Total reclassifications for the period	$ (1,812)	$ (1,851)

Asset Impairment - Summary of

Asset Impairment - Summary of Impairments Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 220,025	$ 6,583
Central Basin Platform
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	187,043	0
Delaware Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	21,288	4,330
San Juan Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	7,519	0
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	4,135	2,005
San Juan Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 40	$ 248

Asset Impairment - Additional

Asset Impairment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 220,025	$ 6,583
Price curve, term	5 years
Increase (decrease) in carrying amount of properties, percent	3.00%
Oil
Impaired Long-Lived Assets Held and Used [Line Items]
Increase (decrease) in carrying amount of properties, percent	(5.00%)
Natural Gas
Impaired Long-Lived Assets Held and Used [Line Items]
Increase (decrease) in carrying amount of properties, percent	(4.00%)
Permian Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 208,300	4,300
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	4,135	2,005
San Juan Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	7,519	0
San Juan Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 40	$ 248

Acquisition and Dispositions of

Acquisition and Dispositions of Properties - Additional Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014MMBoe
Gas and Oil Acreage [Line Items]
Payment for unproved leasehold	$ 7.6		$ 85.7
San Juan Basin
Gas and Oil Acreage [Line Items]
Amount of consideration received		$ 395
Purchase price adjustments		11
Pre-tax proceeds		384
Transaction costs		2.8
Proved developed reserves (MMBOE) | MMBoe				69.038
San Juan | San Juan Basin
Gas and Oil Acreage [Line Items]
Pre-tax gain on disposal		$ 27

Acquisition and Disposition o63

Acquisition and Disposition of Properties - Held for Sale Properties by Major Classes of Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and natural gas properties	$ 571,535
Less accumulated depreciation, depletion and amortization	(388,301)
Total assets held for sale	183,234
Other long-term liabilities	(14,102)
Total liabilities held for sale	(14,102)	$ (12,789)
Total net assets held for sale	169,132
Permian Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and natural gas properties	260,253
Less accumulated depreciation, depletion and amortization	(166,254)
Total assets held for sale	93,999
Other long-term liabilities	(1,086)
Total liabilities held for sale	(1,086)
Total net assets held for sale	92,913
San Juan Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Inventories		3,651
Oil and natural gas properties	311,282	305,386
Less accumulated depreciation, depletion and amortization	(222,047)	(219,059)
Other property and equipment, net		3,761
Total assets held for sale	89,235	93,739
Other long-term liabilities	(13,016)	(12,789)
Total liabilities held for sale	(13,016)	(12,789)
Total net assets held for sale	$ 76,219	$ 80,950