Coterra Energy (CTRA) 10-K 22 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 12, 2016	Jun. 30, 2015
Document and Entity Information
Entity Registrant Name	CABOT OIL & GAS CORP
Entity Central Index Key	858,470
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		414,060,202
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 13

CONSOLIDATED BALANCE SHEET

CONSOLIDATED BALANCE SHEET - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 514	$ 20,954
Accounts receivable, net	120,229	235,397
Income taxes receivable	4,323	3,612
Inventories	17,049	14,026
Derivative instruments	0	137,603
Other current assets	2,671	1,855
Total current assets	144,786	413,447
Properties and equipment, net (Successful efforts method)	4,976,879	4,925,711
Equity method investments	103,517	68,029
Other assets	36,717	30,529
TOTAL ASSETS	5,261,899	5,437,716
Current liabilities
Accounts payable	160,407	400,076
Current portion of long-term debt	20,000	0
Accrued liabilities	24,923	32,992
Interest payable	30,222	30,677
Deferred income taxes	0	35,273
Total current liabilities	235,552	499,018
Postretirement benefits	35,293	35,827
Long-term debt	2,005,000	1,752,000
Deferred income taxes	807,236	843,876
Asset retirement obligations	143,606	124,655
Other liabilities	26,024	39,607
Total liabilities	$ 3,252,711	$ 3,294,983
Commitments and contingencies
Stockholders' equity
Common stock: Authorized -- 960,000,000 shares of $0.10 par value in 2015 and 2014 Issued - 423,768,593 and 422,915,258 shares in 2015 and 2014, respectively	$ 42,377	$ 42,292
Additional paid-in capital	721,997	710,432
Retained earnings	1,552,014	1,698,995
Accumulated other comprehensive income (loss)	(365)	(2,151)
Less treasury stock, at cost: 9,892,680 shares in 2015 and 2014, respectively	(306,835)	(306,835)
Total stockholders' equity	2,009,188	2,142,733
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 5,261,899	$ 5,437,716

CONSOLIDATED BALANCE SHEET (Par

CONSOLIDATED BALANCE SHEET (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Common stock, authorized (in shares)	960,000,000	960,000,000
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, issued (in shares)	423,768,593	422,915,258
Treasury stock (in shares)	9,892,680	9,892,680

CONSOLIDATED STATEMENT OF OPERA

CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING REVENUES
Natural gas	$ 1,025,044	$ 1,590,625	$ 1,405,262
Crude oil and condensate	248,211	313,889	291,418
Gain (loss) on derivative instruments	56,686	219,319	0
Brokered natural gas	16,383	34,416	36,450
Other	10,826	14,762	13,148
TOTAL OPERATING REVENUES	1,357,150	2,173,011	1,746,278
OPERATING EXPENSES
Direct operations	140,814	145,529	140,856
Transportation and gathering	427,588	349,321	229,489
Brokered natural gas	12,592	30,030	29,936
Taxes other than income	42,809	47,012	43,045
Exploration	27,460	28,746	18,165
Depreciation, depletion and amortization	622,211	632,760	651,052
Impairment of oil and gas properties	114,875	771,037	0
General and administrative	69,444	82,590	104,606
TOTAL OPERATING EXPENSES	1,457,793	2,087,025	1,217,149
Earnings (loss) on equity method investments	6,415	3,080	1,102
Gain (loss) on sale of assets	3,866	17,120	21,351
INCOME (LOSS) FROM OPERATIONS	(90,362)	106,186	551,582
Interest expense	96,911	73,785	66,044
Income (loss) before income taxes	(187,273)	32,401	485,538
Income tax expense (benefit)	(73,382)	(72,067)	205,765
NET INCOME (LOSS)	$ (113,891)	$ 104,468	$ 279,773
Earnings (loss) per share
Basic (in dollars per share)	$ (0.28)	$ 0.25	$ 0.67
Diluted (in dollars per share)	$ (0.28)	$ 0.25	$ 0.66
Weighted-average common shares outstanding
Basic (in shares)	413,696	415,840	420,188
Diluted (in shares)	413,696	417,601	422,375
Dividends per common share (in dollars per share)	$ 0.08	$ 0.08	$ 0.06

CONSOLIDATED STATEMENT OF COMPR

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)		$ (113,891)	$ 104,468	$ 279,773
Other comprehensive income (loss), net of taxes:
Reclassification adjustment for settled cash flow hedge contracts	[1]	0	86,726	(34,548)
Changes in fair value of cash flow hedge contracts	[2]	0	(80,175)	(2,720)
Postretirement benefits:
Net gain (loss)	[3]	1,786	(325)	4,641
Amortization of net (gain) loss	[4]	0	(16)	386
Total other comprehensive income (loss)		1,786	6,210	(32,241)
Comprehensive income (loss)		$ (112,105)	$ 110,678	$ 247,532
[1]	Net of income taxes of $(57,477) and $22,454 for the year ended December 31, 2014 and 2013, respectively.
[2]	Net of income taxes of $53,135 and $1,803 for the year ended December 31, 2014 and 2013, respectively.
[3]	Net of income taxes of $(1,043), $48 and $(2,977) for the year ended December 31, 2015, 2014 and 2013, respectively.
[4]	Net of income taxes of $10 and $(255) for the year ended December 31, 2014 and 2013, respectively.

CONSOLIDATED STATEMENT OF COMP6

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Reclassification adjustment for settled hedge contracts, income taxes		$ (57,477)	$ 22,454
Changes in fair value of hedge contracts, income taxes		53,135	1,803
Postretirement benefits:
Net gain / (loss), income taxes	$ (1,043)	48	(2,977)
Amortization of net loss, income taxes		$ 10	$ (255)

CONSOLIDATED STATEMENT OF CASH

CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ (113,891)	$ 104,468	$ 279,773
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation, depletion and amortization	622,211	632,760	651,052
Impairment of oil and gas properties	114,875	771,037	0
Deferred income tax expense (benefit)	(72,968)	(112,567)	138,380
(Gain) loss on sale of assets	(3,866)	(17,120)	(21,351)
Exploratory dry hole cost	3,452	7,907	808
(Gain) loss on derivative instruments	(56,686)	(219,319)	0
Net cash received (paid) in settlement of derivative instruments	194,289	81,716	0
Earnings of equity method investments	(6,415)	(3,080)	(1,102)
Amortization of debt issuance costs	4,454	4,754	3,693
Stock-based compensation and other	13,645	21,429	46,965
Changes in assets and liabilities:
Accounts receivable, net	112,406	(11,689)	(49,398)
Income taxes	(711)	(34,282)	29,002
Inventories	(3,023)	3,441	(3,033)
Other current assets	(817)	733	(428)
Accounts payable and accrued liabilities	(64,533)	2,883	(22,908)
Other assets and liabilities	(1,685)	1,989	(8,014)
Stock-based compensation tax benefit	0	1,375	(18,913)
Net cash provided by operating activities	740,737	1,236,435	1,024,526
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(955,602)	(1,479,632)	(1,194,739)
Acquisitions	(16,312)	(214,737)	0
Proceeds from sale of assets	7,653	39,492	323,501
Restricted cash	0	28,094	(28,094)
Investment in equity method investments	(29,073)	(38,057)	(18,875)
Net cash used in investing activities	(993,334)	(1,664,840)	(918,207)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings from debt	877,000	2,032,000	955,000
Repayments of debt	(604,000)	(1,427,000)	(895,000)
Treasury stock repurchases	0	(138,852)	(164,634)
Dividends paid	(33,090)	(33,278)	(25,232)
Stock-based compensation tax benefit	0	(1,375)	18,913
Capitalized debt issuance costs	(7,838)	(5,626)	(2,750)
Other	85	90	48
Net cash provided by (used in) financing activities	232,157	425,959	(113,655)
Net decrease in cash and cash equivalents	(20,440)	(2,446)	(7,336)
Cash and cash equivalents, beginning of period	20,954	23,400	30,736
Cash and cash equivalents, end of period	$ 514	$ 20,954	$ 23,400

CONSOLIDATED STATEMENT OF STOCK

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at beginning of period at Dec. 31, 2012	$ 2,131,447	$ 42,086	$ (3,349)	$ 695,566	$ 23,880	$ 1,373,264
Balance (in shares) at Dec. 31, 2012		420,861,000	808,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	279,773					279,773
Exercise of stock appreciation rights	(13,226)	$ 38		(13,264)
Exercise of stock appreciation rights (in shares)		382,000
Stock amortization and vesting	9,802	$ 77		9,725
Stock amortization and vesting (in shares)		772,000
Tax benefit of stock-based compensation	18,913			18,913
Purchase of treasury stock	$ (164,634)		$ (164,634)
Purchase of treasury stock (in shares)	4,800,000		4,810,000
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (25,232)					(25,232)
Other comprehensive income (loss)	(32,241)				(32,241)
Balance at end of period at Dec. 31, 2013	2,204,602	$ 42,201	$ (167,983)	710,940	(8,361)	1,627,805
Balance (in shares) at Dec. 31, 2013		422,015,000	5,618,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	104,468					104,468
Stock amortization and vesting	958	$ 91		867
Stock amortization and vesting (in shares)		900,000
Tax benefit of stock-based compensation	(1,375)			(1,375)
Purchase of treasury stock	$ (138,852)		$ (138,852)
Purchase of treasury stock (in shares)	4,300,000		4,275,000
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (33,278)					(33,278)
Other comprehensive income (loss)	6,210				6,210
Balance at end of period at Dec. 31, 2014	2,142,733	$ 42,292	$ (306,835)	710,432	(2,151)	1,698,995
Balance (in shares) at Dec. 31, 2014		422,915,000	9,893,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(113,891)					(113,891)
Exercise of stock appreciation rights	(942)	$ 4		(946)
Exercise of stock appreciation rights (in shares)		40,000
Stock amortization and vesting	$ 12,592	$ 81		12,511
Stock amortization and vesting (in shares)		814,000
Purchase of treasury stock (in shares)	0
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (33,090)					(33,090)
Other comprehensive income (loss)	1,786				1,786
Balance at end of period at Dec. 31, 2015	$ 2,009,188	$ 42,377	$ (306,835)	$ 721,997	$ (365)	$ 1,552,014
Balance (in shares) at Dec. 31, 2015		423,769,000	9,893,000

CONSOLIDATED STATEMENT OF STOC9

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Cash dividends, per share (in dollars per share)	$ 0.08	$ 0.08	$ 0.06

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Nature of Operations Cabot Oil & Gas Corporation and its subsidiaries (the Company) are engaged in the development, exploitation, exploration, production and marketing of natural gas, oil and, to a lesser extent, NGLs exclusively within the continental United States. The Company also transports, stores, gathers and purchases natural gas for resale. The Company's exploration and development activities are concentrated in areas with known hydrocarbon resources, which are conducive to multi-well, repeatable drilling programs. The Company operates in one segment, natural gas and oil development, exploitation and exploration. The Company's oil and gas properties are managed as a whole rather than through discrete operating segments or business units. Operational information is tracked by geographic area; however, financial performance is assessed as a single enterprise and not on a geographic basis. Allocation of resources is made on a project basis across the Company's entire portfolio without regard to geographic areas. The consolidated financial statements include the accounts of the Company and its subsidiaries after eliminating all significant intercompany balances and transactions. Certain reclassifications have been made to prior year statements to conform with current year presentation. These reclassifications have no impact on previously reported net income (loss). Significant Accounting Policies Cash and Cash Equivalents The Company considers all highly liquid short-term investments with a maturity of three months or less and deposits in money market funds that are readily convertible to cash to be cash equivalents. Cash and cash equivalents were primarily concentrated in one financial institution at December 31, 2015 and 2014 . The Company periodically assesses the financial condition of its financial institutions and considers any possible credit risk to be minimal. Allowance for Doubtful Accounts The Company records an allowance for doubtful accounts for receivables that the Company determines to be uncollectible based on the specific identification method. Inventories Inventories are comprised of natural gas in storage, tubular goods and well equipment and pipeline imbalances. Natural gas in storage and tubular goods and well equipment balances are carried at average cost. Natural gas gathering and pipeline operations normally include imbalance arrangements with the pipeline. The volumes of natural gas due to or from the Company under imbalance arrangements are recorded at actual selling or purchase prices, as the case may be, and are adjusted monthly to market prices. Equity Method Investments The Company accounts for its investments in entities over which the Company has significant influence, but not control, using the equity method of accounting. Under the equity method of accounting, the Company increases its investment for contributions made and records its proportionate share of net earnings, declared dividends and partnership distributions based on the most recently available financial statements of the investee. The Company records the activity for its equity method investments on a one month lag. In addition, the Company evaluates its equity method investments for potential impairment whenever events or changes in circumstances indicate that there is an other-than-temporary decline in the value of the investment. Properties and Equipment The Company uses the successful efforts method of accounting for oil and gas producing activities. Under this method, acquisition costs for proved and unproved properties are capitalized when incurred. Exploration costs, including geological and geophysical costs, the costs of carrying and retaining unproved properties and exploratory dry hole drilling costs, are expensed. Development costs, including the costs to drill and equip development wells and successful exploratory drilling costs to locate proved reserves are capitalized. Exploratory drilling costs are capitalized when incurred pending the determination of whether a well has found proved reserves. The determination is based on a process which relies on interpretations of available geologic, geophysical, and engineering data. If a well is determined to be successful, the capitalized drilling costs will be reclassified as part of the cost of the well. If a well is determined to be unsuccessful, the capitalized drilling costs will be charged to exploration expense in the Consolidated Statement of Operations in the period the determination is made. If an exploratory well requires a major capital expenditure before production can begin, the cost of drilling the exploratory well will continue to be carried as an asset pending determination of whether reserves have been found only as long as: (i) the well has found a sufficient quantity of reserves to justify its completion as a producing well if the required capital expenditure is made and (ii) drilling of an additional exploratory well is under way or firmly planned for the near future. If drilling in the area is not under way or firmly planned, or if the well has not found a commercially producible quantity of reserves, the exploratory well is assumed to be impaired and its costs are charged to exploration expense. Development costs of proved oil and gas properties, including estimated dismantlement, restoration and abandonment costs and acquisition costs, are depreciated and depleted on a field basis by the units-of-production method using proved developed and proved reserves, respectively. Properties related to gathering and pipeline systems and equipment are depreciated using the straight-line method based on estimated useful lives ranging from 10 to 25 years. Generally pipeline and transmission systems are depreciated over 12 to 25 years, gathering and compression equipment is depreciated over 10 years and storage equipment and facilities are depreciated over 10 to 16 years. Buildings are depreciated on a straight-line basis over 25 to 40 years. Certain other assets are depreciated on a straight-line basis over 3 to 10 years. Costs of retired, sold or abandoned properties that make up a part of an amortization base (partial field) are charged to accumulated depreciation, depletion and amortization if the units-of-production rate is not significantly affected. A gain or loss, if any, is recognized only when a group of proved properties (entire field) that make up the amortization base has been retired, abandoned or sold. The Company evaluates its proved oil and gas properties for impairment whenever events or changes in circumstances indicate an asset's carrying amount may not be recoverable. The Company compares expected undiscounted future cash flows to the net book value of the asset. If the future undiscounted expected cash flows, based on estimates of future natural gas and crude oil prices, operating costs and anticipated production from proved reserves and risk-adjusted probable and possible reserves, are lower than the net book value of the asset, the capitalized cost is reduced to fair value. Commodity pricing is estimated by using a combination of assumptions management uses in its budgeting and forecasting process as well as historical and current prices adjusted for geographical location and quality differentials, as well as other factors that management believes will impact realizable prices. Fair value is calculated by discounting the future cash flows. The discount factor used is based on rates utilized by market participants that are commensurate with the risks inherent in the development and production of the underlying natural gas and oil. Unproved oil and gas properties are assessed periodically for impairment on an aggregate basis through periodic updates to the Company's undeveloped acreage amortization based on past drilling and exploration experience, the Company's expectation of converting leases to held by production and average property lives. Average property lives are determined on a geographical basis and based on the estimated life of unproved property leasehold rights. During 2015 , 2014 and 2013 , amortization associated with the Company's unproved properties was $41.4 million , $17.4 million and $53.6 million , respectively, and is included in depreciation, depletion, and amortization in the Consolidated Statement of Operations. Asset Retirement Obligations The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred if a reasonable estimate of fair value can be made. The associated asset retirement cost is capitalized as part of the carrying amount of the long-lived asset. The asset retirement costs are depreciated using the units-of-production method. The majority of the asset retirement obligations recorded by the Company relate to the plugging and abandonment of oil and gas wells. However, liabilities are also recorded for meter stations, pipelines, processing plants and compressors. At December 31, 2015 , there were no assets legally restricted for purposes of settling asset retirement obligations. Additional retirement obligations increase the liability associated with new oil and gas wells and other facilities as these obligations are incurred. Accretion expense is included in depreciation, depletion and amortization expense in the Consolidated Statement of Operations. Derivative Instruments and Hedging Activities The Company enters into derivative contracts, primarily options and swaps, to manage its exposure to price fluctuations on a portion of its anticipated future natural gas and oil production. The Company’s credit agreement restricts the ability of the Company to enter into commodity derivatives other than to hedge or mitigate risks to which the Company has actual or projected exposure or as permitted under the Company’s risk management policies and where such derivatives do not subject the Company to material speculative risks. All of the Company’s derivatives are used for risk management purposes and are not held for trading purposes. All derivatives are recognized on the balance sheet and are measured at fair value. At the end of each quarterly period, these derivatives are marked-to-market. If the derivative does not qualify or is not designated as a cash flow hedge, changes in the fair value of the derivative are recognized in income. If the derivative qualifies and is designated as a cash flow hedge, changes in the fair value of the derivative are deferred in accumulated other comprehensive income to the extent the hedge is effective. For derivatives that qualify and are designated as a cash flow hedges, the hedging relationship between the hedging instruments and hedged items must be highly effective in achieving the offset of changes in cash flows attributable to the hedged risk, both at the inception of the hedge and on an ongoing basis. The Company measures hedge effectiveness on a quarterly basis. Hedge accounting is discontinued prospectively if and when a hedging instrument becomes ineffective. Gains and losses deferred in accumulated other comprehensive income related to cash flow hedges that become ineffective remain unchanged until the related production occurs. If the Company determines that it is probable that a forecasted hedged transaction will not occur, deferred gains or losses on the related hedging instrument are recognized in income immediately. Gains and losses on derivatives designated as cash flow hedges are included in natural gas and crude oil and condensate revenues. Gains and losses on derivatives which represent hedge ineffectiveness and gains and losses on derivatives not designated or that do not qualify for hedge accounting are included in operating revenues in gain (loss) on derivative instruments. The resulting cash flows are reported as cash flows from operating activities. Fair Value of Assets and Liabilities The Company follows the authoritative accounting guidance for measuring fair value of assets and liabilities in its financial statements. 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). The Company utilizes market data or assumptions that market participants who are independent, knowledgeable and willing and able to transact would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. The Company is able to classify fair value balances based on the observability of these inputs. The authoritative guidance for fair value measurements establishes three levels of the fair value hierarchy, defined as follows: • Level 1: Unadjusted, quoted prices for identical assets or liabilities in active markets. • Level 2: Quoted prices in markets that are not considered to be active or financial instruments for which all significant inputs are observable, either directly or indirectly for substantially the full term of the asset or liability. • Level 3: Significant, unobservable inputs for use when little or no market data exists, requiring a significant degree of judgment. The hierarchy gives the highest priority to Level 1 measurements and the lowest priority to Level 3 measurements. Depending on the particular asset or liability, input availability can vary depending on factors such as product type, longevity of a product in the market and other particular transaction conditions. In some cases, certain inputs used to measure fair value may be categorized into different levels of the fair value hierarchy. For disclosure purposes under the accounting guidance, the lowest level that contains significant inputs used in the valuation should be chosen. Revenue Recognition Natural gas and oil sales result from interests in oil and gas properties owned by the Company. Sales of natural gas and oil are recognized when the product is delivered and title transfers to the purchaser. Payment is generally received one to three months after the sale has occurred. Producer Gas Imbalances. The Company applies the sales method of accounting for natural gas revenue. Under this method, revenues are recognized based on the actual volume of natural gas sold to purchasers. Natural gas production operations may include joint owners who take more or less than the production volumes entitled to them on certain properties. Production volume is monitored to minimize these natural gas imbalances. Under this method, a natural gas imbalance liability is recorded if the Company's excess takes of natural gas exceed its estimated remaining proved developed reserves for these properties at the actual price realized upon the gas sale. A receivable is recognized only to the extent an imbalance cannot be recouped from the reserves in the underlying properties. The Company’s aggregate imbalance positions at December 31, 2015 and 2014 were not material. Brokered Natural Gas. Revenues and expenses related to brokering natural gas are reported gross as part of operating revenues and operating expenses in accordance with applicable accounting standards. The Company buys and sells natural gas utilizing separate purchase and sale transactions, typically with separate counterparties, whereby the Company and/or the counterparty takes title to the natural gas purchased or sold. Income Taxes The Company follows the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recorded for the estimated future tax consequences attributable to the differences between the financial carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using the tax rate in effect for the year in which those temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the year of the enacted rate change. A valuation allowance is established to reduce deferred tax assets if it is more likely than not that the related tax benefits will not be realized. The Company is required to make judgments, including estimating reserves for potential adverse outcomes regarding tax positions that the Company has taken. The Company accounts for uncertainty in income taxes using a recognition and measurement threshold for tax positions taken or expected to be taken in a tax return. The tax benefit from an uncertain tax position is recognized when it is more likely than not that the position will be sustained upon examination by taxing authorities based on technical merits of the position. The amount of the tax benefit recognized is the largest amount of the benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The effective tax rate and the tax basis of assets and liabilities reflect management's estimates of the ultimate outcome of various tax uncertainties. The Company recognizes accrued interest related to uncertain tax positions in interest expense and accrued penalties related to such positions in general and administrative expense in the Consolidated Statement of Operations. Stock-Based Compensation The Company accounts for stock-based compensation under the fair value method of accounting. Under this method, compensation cost is measured at the grant date for equity-classified awards and remeasured each reporting period for liability-classified awards based on the fair value of an award and is recognized over the service period, which is generally the vesting period. To calculate fair value, the Company uses either a Monte Carlo or Black-Scholes valuation model depending on the specific provisions of the award. Stock-based compensation cost for all types of awards is included in general and administrative expense in the Consolidated Statement of Operations. The tax benefit for stock-based compensation is included as both a cash outflow from operating activities and a cash inflow from financing activities in the Consolidated Statement of Cash Flows. The Company recognizes a tax benefit only to the extent it reduces the Company's income taxes payable. Environmental Matters Environmental expenditures are expensed or capitalized, as appropriate, depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations, and that do not have future economic benefit are expensed. Liabilities related to future costs are recorded on an undiscounted basis when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated. Any insurance recoveries are recorded as assets when received. Credit and Concentration Risk Substantially all of the Company's accounts receivable result from the sale of natural gas and oil and joint interest billings to third parties in the oil and gas industry. This concentration of purchasers and joint interest owners may impact the Company's overall credit risk, either positively or negatively, in that these entities may be similarly affected by changes in economic or other conditions. The Company does not anticipate any material impact on its financial results due to non-performance by the third parties. During the years ended December 31, 2015 , 2014 and 2013 , two customers accounted for approximately 16% and 14% , two customers accounted for approximately 14% and 10% and four customers accounted for approximately 21% , 16% , 14% and 11% , respectively, of the Company's total sales. The Company does not believe that the loss of any of these customers would have a material adverse effect because alternative customers are readily available. Use of Estimates In preparing financial statements, the Company follows accounting principles generally accepted in the United States. These principles require management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. The most significant estimates pertain to proved natural gas and oil reserves and related cash flow estimates which are used to compute depreciation, depletion and amortization and impairments of proved oil and gas properties. Other significant estimates include natural gas and oil revenues and expenses, fair value of derivative instruments, estimates of expenses related to legal, environmental and other contingencies, asset retirement obligations, postretirement obligations, stock-based compensation and deferred income taxes. Actual results could differ from those estimates. Recently Adopted Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2015-17, Balance Sheet Classification of Deferred Taxes. The amendments in this update require deferred tax liabilities and assets to be classified as noncurrent. The guidance is effective for interim and annual periods beginning after December 15, 2016, however early adoption is allowed. This update may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The Company elected to early adopt this standard on a prospective basis and, as a result, there have been no adjustments made to prior periods. The adoption of this guidance only affected the Company's financial position and did not have an impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In March 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. The amendments in this update require 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 recognition and measurement guidance for debt issuance costs are not affected by the amendments in this update. In August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements. The update provides authoritative guidance for debt issuance costs related to line-of-credit arrangements, noting the SEC staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. The guidance is effective for interim and annual periods beginning after December 15, 2015. The Company does not believe the adoption of this guidance will have a material effect on its financial position, results of operations or cash flows. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, as a new Topic, Accounting Standards Codification Topic 606. The new revenue recognition standard provides a five-step analysis of transactions to determine when and how revenue is recognized. The core principle of the guidance is that a company should recognize revenue to depict the transfer of promised 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. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606), which deferred the effective date of ASU No. 2014-09 by one year, making the new standard effective for interim and annual periods beginning after December 15, 2017. This ASU can be adopted either retrospectively or as a cumulative-effect adjustment as of the date of adoption; however, entities reporting under U.S. GAAP are not permitted to adopt the standard earlier than the original effective date for public entities (that is, no earlier than 2017 for calendar year-end entities). The Company is currently evaluating the effect that adopting this guidance will have on its financial position, results of operations or cash flows.

Acquisitions and Divestitures

Acquisitions and Divestitures	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions and Divestitures	Acquisitions and Divestitures Acquisitions In December 2014, the Company completed the acquisition of certain proved and unproved oil and gas properties in the Eagle Ford Shale in south Texas for approximately $30.5 million . Total net cash consideration paid by the Company was approximately $29.9 million , which reflects the impact of customary purchase price adjustments and acquisition costs. In October 2014, the Company completed the acquisition of certain proved and unproved oil and gas properties in the Eagle Ford Shale in south Texas. Total net cash consideration paid by the Company was approximately $185.2 million , which reflects the purchase price of $210.0 million , adjusted by approximately $17.4 million for properties that the seller was unable to obtain consents for certain leaseholds prior to closing and approximately $7.4 million for the impact of customary purchase price adjustments and acquisition costs. In addition, the Company also assumed a liability of approximately $1.2 million related to asset retirement obligations of the wells acquired. In April 2015, the Company completed the acquisition of the remaining oil and gas properties for which the seller was unable to obtain consents at closing for approximately $16.0 million . The Company accounted for these transactions as an asset purchase, whereby the identifiable assets acquired were recorded at cost, with the respective assigned carrying amount based on the relative fair value of the unproved and proved properties at the acquisition date. The fair value measurement of assets acquired was based on inputs that are not observable in the market and therefore represent Level 3 inputs. The fair value of oil and gas properties were measured using discounted future cash flows. The discount factor used was based on rates utilized by market participants that are commensurate with the risks inherent in the development and production of the underlying natural gas and oil. Significant inputs to the valuation of oil and gas properties include (i) reserves, including risk adjustments for probable and possible reserves; (ii) production rates based on the Company's experience with similar properties in which it operates; (iii) estimated future operating and development costs; (iv) future commodity prices; (v) future cash flows; and (vi) a market-based weighted average cost of capital rate of 10.0% . Divestitures The Company recognized an aggregate net gain (loss) on sale of assets of $3.9 million , $17.1 million and $21.4 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. In October 2014, the Company completed the divestiture of certain proved and unproved oil and gas properties in east Texas to a third party for approximately $44.3 million and recognized a $19.9 million gain on sale of assets. In December 2013, the Company sold certain proved and unproved oil and gas properties located in the Oklahoma and Texas panhandles to Chaparral Energy, L.L.C. for approximately $160.0 million and recognized a $19.4 million gain on sale of assets. The Company also sold certain proved and unproved oil and gas properties located in Oklahoma, Texas and Kansas to a third party for approximately $123.4 million and recognized a $17.5 million loss on sale of assets. In 2013, the Company sold various other proved and unproved oil and gas properties for approximately $44.3 million and recognized an aggregate net gain of $19.5 million .

Properties and Equipment, Net

Properties and Equipment, Net	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Properties and Equipment, Net	Properties and Equipment, Net Properties and equipment, net are comprised of the following: December 31, (In thousands) 2015 2014 Proved oil and gas properties $ 8,821,146 $ 7,984,979 Unproved oil and gas properties 390,434 492,208 Gathering and pipeline systems 243,672 241,272 Land, building and other equipment 117,848 109,758 9,573,100 8,828,217 Accumulated depreciation, depletion and amortization (4,596,221 ) (3,902,506 ) $ 4,976,879 $ 4,925,711 Impairment In December 2015, the Company recorded an impairment of $114.9 million associated with oil and gas properties in certain non-core fields in south Texas, east Texas and Louisiana . The impairment of these fields was due to a significant decline in commodity prices in late 2015. These fields were reduced to fair value of approximately $89.9 million using discounted future cash flows. In December 2014, the Company recorded a $771.0 million impairment of oil and gas properties in certain non-core fields, primarily in east Texas. The impairment of these fields was due to a significant decline in commodity prices in late 2014 and management's decision not to pursue any further activity in these non-core areas in the current price environment. These fields were reduced to fair value of approximately $86.5 million using discounted future cash flows. The fair value of the impaired fields was based on significant inputs that were not observable in the market and are considered to be Level 3 inputs as defined by ASC 820. Refer to Note 1 for a description of fair value hierarchy. Key assumptions included (i) reserves, including risk adjustments for probable and possible reserves; (ii) production rates based on the Company's experience with similar properties in which it operates; (iii) estimated future operating and development costs; (iv) future commodity prices; (v) future cash flows; and (vi) a market-based weighted average cost of capital rate of 10% at December 31, 2015 and 2014, respectively. Capitalized Exploratory Well Costs The following table reflects the net changes in capitalized exploratory well costs: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of period $ 10,557 $ — $ 10,390 Additions to capitalized exploratory well costs pending the determination of proved reserves — 10,557 — Reclassifications to wells, facilities, and equipment based on the determination of proved reserves (10,557 ) — (10,198 ) Capitalized exploratory well costs charged to expense — — (192 ) Balance at end of period $ — $ 10,557 $ — The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed: December 31, (In thousands) 2015 2014 2013 Capitalized exploratory well costs that have been capitalized for a period of one year or less $ — $ 10,557 $ — Capitalized exploratory well costs that have been capitalized for a period greater than one year — — — $ — $ 10,557 $ —

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments The Company has two equity method investments, Constitution Pipeline Company, LLC (Constitution) and Meade Pipeline Co LLC (Meade), which are further described below. Activity related to these equity method investments is as follows: Constitution Meade Total Year Ended December 31, Year Ended December 31, Year Ended December 31, (In thousands) 2015 2014 2013 2015 2014 2013 2015 2014 2013 Balance at beginning of period $ 64,268 $ 26,892 $ 6,915 $ 3,761 $ — $ — $ 68,029 $ 26,892 $ 6,915 Contributions 19,625 34,200 18,875 9,448 3,857 — 29,073 38,057 18,875 Earnings (loss) on equity method investments 6,452 3,176 1,102 (37 ) (96 ) — 6,415 3,080 1,102 Balance at end of period $ 90,345 $ 64,268 $ 26,892 $ 13,172 $ 3,761 $ — $ 103,517 $ 68,029 $ 26,892 Constitution Pipeline Company, LLC In April 2012, the Company acquired a 25% equity interest in Constitution, which was formed to develop, construct and operate a 124 mile large diameter pipeline to transport natural gas from northeast Pennsylvania to both the New England and New York markets. Under the terms of the agreement, the Company agreed to invest its proportionate share of costs associated with the development and construction of the pipeline and related facilities, subject to a contribution cap of $250 million . The expected in-service date for the new pipeline is the fourth quarter of 2016; however, this estimate is contingent on the timely issuance of remaining outstanding permits. The Company expects to contribute approximately $139.0 million over the next two years . Meade Pipeline Co LLC In February 2014, the Company acquired a 20% equity interest in Meade, which was formed to participate in the development and construction of a 177 -mile pipeline (Central Penn Line) that will transport natural gas from Susquehanna County, Pennsylvania to an interconnect with Transcontinental Gas Pipe Line Company, LLC’s (Transco) mainline in Lancaster County, Pennsylvania. The new pipeline will be constructed and operated by Transco and will be owned by Transco and Meade in proportion to their respective ownership percentages of approximately 61% and 39% , respectively. Under the terms of the Meade LLC agreement, the Company agreed to invest its proportionate share of Meade’s anticipated costs associated with the new pipeline. The Company expects to contribute approximately $130.2 million over the next two years . The expected in-service date for the new pipeline is scheduled for the second half of 2017.

Debt and Credit Agreements

Debt and Credit Agreements	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt and Credit Agreements	Debt and Credit Agreements The Company's debt and credit agreements consisted of the following: December 31, (In thousands) 2015 2014 Total debt 7.33% weighted-average senior notes $ 20,000 $ 20,000 6.51% weighted-average senior notes 425,000 425,000 9.78% senior notes 67,000 67,000 5.58% weighted-average senior notes 175,000 175,000 3.65% weighted-average senior notes 925,000 925,000 Revolving credit facility 413,000 140,000 Current maturities 7.33% weighted-average senior notes (20,000 ) — Long-term debt, excluding current maturities $ 2,005,000 $ 1,752,000 The Company has debt maturities of $20.0 million due in 2016, $312.0 million due in 2018 and $100.0 million due in 2020. In addition, the revolving credit facility matures in 2020 . No other tranches of debt are due within the next five years. At December 31, 2015 , the Company was in compliance with all restrictive financial covenants, as amended, for both its revolving credit facility and senior notes. Senior Notes The Company has various issuances of senior notes. Interest on each of the senior notes is payable semi-annually. Under the terms of the various senior note agreements, the Company may prepay all or any portion of the notes of each series on any date at a price equal to the principal amount thereof plus accrued and unpaid interest plus a make-whole premium. Due to the significant decrease in natural gas and crude oil prices during 2015 and the related impact on certain of the Company's financial covenants, effective December 31, 2015, the Company amended the agreements governing its senior notes to adjust certain financial covenants and to include an additional financial covenant, as further described below. The amended agreements provide that the asset coverage ratio (present value of proved reserves to debt, as defined in the agreements) be calculated based on the present value of proved reserves before income taxes, whereas prior to these amendments, the present value was calculated after income taxes. The minimum asset coverage ratio was also reduced from 1.75 to 1.0 to 1.25 to 1.0 through and including December 31, 2017 and increases back to the pre-amended ratio of 1.75 to 1.0 beginning on January 1, 2018 and thereafter. The amendments also introduce a leverage ratio covenant, which is defined in the agreement as the ratio of debt to consolidated EBITDAX. The leverage ratio may not exceed a maximum ratio of: • 4.75 to 1.0 through and including December 31, 2016; • 4.25 to 1.0 through and including December 31, 2017; and • 3.50 to 1.0 beginning on March 31, 2018 and remains in effect until the Company maintains a leverage ratio below 3.0 to 1.0 for two consecutive fiscal quarters ending on or after December 31, 2017, or receives an investment grade rating by Standard & Poor's Ratings Services (S&P) or Moody’s Investor Service, Inc (Moody's). In addition, the amendments provide for potential increases to the original coupon rates ranging from 0 to 125 basis points depending on the asset coverage and leverage ratios at the end of the respective quarterly period, as defined in the note agreements. These potential increases lapse when the Company maintains a leverage ratio between 3.0 to 1.0 for two consecutive fiscal quarters ending on or after December 31, 2017 or receives an investment grade rating by S&P or Moody's. As of December 31, 2015, based on the Company's asset coverage and leverage ratios, there were no interest rate adjustments required for the Company's senior notes. The note agreements continue to include a minimum annual coverage ratio of consolidated cash flow to interest expense for the trailing four quarters of 2.8 to 1.0, which was unchanged by the amendments. There are also various other covenants customarily found in such debt instruments. The notes are also subject to customary events of default. In conjunction with the execution of the amendments, the Company incurred approximately $1.9 million of debt issuance costs, which were capitalized and are being amortized over the term of the respective amended agreements in accordance with ASC 470-50, “Debt Modifications and Extinguishments.” 7.33% Weighted-Average Senior Notes In July 2001, the Company issued $170 million of senior unsecured notes to a group of seven institutional investors in a private placement. The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 75,000,000 10 years July 2011 7.26 % Tranche 2 $ 75,000,000 12 years July 2013 7.36 % Tranche 3 $ 20,000,000 15 years July 2016 7.46 % As of December 31, 2015 , the Company has repaid $150 million of aggregate maturities associated with the 7.33% weighted-average senior notes. 6.51% Weighted-Average Senior Notes In July 2008, the Company issued $425 million of senior unsecured notes to a group of 41 institutional investors in a private placement. The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 245,000,000 10 years July 2018 6.44 % Tranche 2 $ 100,000,000 12 years July 2020 6.54 % Tranche 3 $ 80,000,000 15 years July 2023 6.69 % 9.78% Senior Notes In December 2008, the Company issued $67 million aggregate principal amount of 10 year 9.78% senior unsecured notes to a group of four institutional investors in a private placement. 5.58% Weighted-Average Senior Notes In December 2010, the Company issued $175 million of senior unsecured notes to a group of eight institutional investors in a private placement. The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 88,000,000 10 years January 2021 5.42 % Tranche 2 $ 25,000,000 12 years January 2023 5.59 % Tranche 3 $ 62,000,000 15 years January 2026 5.80 % 3.65% Weighted‑Average Senior Notes In September 2014, the Company issued $925 million of senior unsecured notes to a group of 24 institutional investors in a private placement. The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 100,000,000 7 years September 2021 3.24 % Tranche 2 $ 575,000,000 10 years September 2024 3.67 % Tranche 3 $ 250,000,000 12 years September 2026 3.77 % In conjunction with the issuance of the 3.65% weighted‑average senior notes in September 2014, the Company incurred approximately $5.6 million of debt issuance costs, which were capitalized and are being amortized over the term of the notes. The amortization of debt issuance costs is included in interest expense in the Consolidated Statement of Operations. Revolving Credit Agreement The Company's revolving credit facility is unsecured. The borrowing base is redetermined annually under the terms of the revolving credit facility on April 1. In addition, either the Company or the banks may request an interim redetermination twice a year or in conjunction with certain acquisitions or sales of oil and gas properties. Effective April 17, 2015, the Company amended its revolving credit facility to extend the maturity date from May 2017 to April 2020 and change the mechanism under which interest rate margins are determined for outstanding borrowings. The revolving credit facility, as amended, provides for a borrowing base of $3.4 billion and commitments of $1.8 billion . The amended credit facility also provides for an accordion feature, which allows the Company to increase the available credit line up to an additional $500 million if one or more of the existing or new banks agree to provide such an increased amount. In conjunction with the Company's amendments to the senior notes, effective December 31, 2015, the Company also amended its revolving credit facility to adjust certain financial covenants and include an additional financial covenant, as further described below. The amendment provides that the asset coverage ratio (present value of proved reserves to debt, as defined in the agreement) be calculated based on the present value of proved reserves before income taxes, whereas prior to the amendment, the present value was calculated after income taxes. The minimum asset coverage ratio was also reduced from 1.75 to 1.0 to 1.25 to 1.0 through and including December 31, 2017 and increases back to the pre-amended ratio of 1.75 to 1.0 beginning on March 31, 2018. The amendment also introduces a leverage ratio covenant, which is defined in the agreement as the ratio of debt to consolidated EBITDAX. The ratio may not exceed a maximum ratio of: • 4.75 to 1.0 through and including December 31, 2016; • 4.25 to 1.0 through and including December 31, 2017; and • 3.50 to 1.0 beginning on March 31, 2018 and remains in effect until the Company maintains a leverage ratio below 3.0 to 1.0 for two consecutive fiscal quarters beginning on or after December 31, 2017, or receives an investment grade rating by S&P or Moody’s. In addition to the amendment to the asset coverage ratio and inclusion of the leverage ratio covenant, the amended revolving credit facility also increases the maximum leverage ratio and associated margins. Interest rates under the amended revolving credit facility are based on LIBOR or ABR indications, plus a margin which ranges from 50 to 300 basis points, as defined in the agreement. These rates will remain in effect (i) until the first date occurring on or after December 31, 2017 on which both the asset coverage ratio is greater than 1.75 to 1.0 and the leverage ratio is less than 3.0 to 1.0 for two consecutive fiscal quarters, at which time the related margins will revert back to pre-amendment levels of 50 to 225 basis points, or (ii) upon the Company achieving an investment grade rating from either Moody's or S&P, at which time the associated margins will be adjusted and determined based on the Company's credit rating on a prospective basis. The revolving credit facility also contains various other customary covenants that remained unchanged as a result of the amendment, which include the following (with all calculations based on definitions contained in the agreement): (a) Maintenance of a minimum annual coverage ratio of consolidated cash flow to interest expense for the trailing four quarters of 2.8 to 1.0. (b) Maintenance of a minimum current ratio of 1.0 to 1.0. The credit facility also provides for a commitment fee on the unused available balance at annual rates ranging from 0.30% to 0.50% . The other terms and conditions of the amended facility are generally consistent with the terms and conditions of the revolving credit facility prior to its amendment. The Company incurred approximately $7.8 million and $1.1 million of debt issuance costs in connection with the April 17, 2015 and December 31, 2015 amendments to the revolving credit facility, respectively, which were capitalized and will be amortized over the term of the amended credit facility. The remaining unamortized costs will be amortized over the term of the amended revolving credit facility in accordance with ASC 470-50, "Debt Modifications and Extinguishments." At December 31, 2015 , the Company had $413.0 million of borrowings outstanding under its revolving credit facility and had unused commitments of $1.4 billion . The Company's weighted-average effective interest rates for the revolving credit facility during the years ended December 31, 2015 , 2014 and 2013 were approximately 2.2% , 2.2% and 2.3% , respectively.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities Through March 31, 2014, the Company elected to designate its commodity derivatives as cash flow hedges for accounting purposes. Effective April 1, 2014, the Company discontinued hedge accounting for its commodity derivatives on a prospective basis. As a result of discontinuing hedge accounting, the unrealized loss included in accumulated other comprehensive income (loss) as of April 1, 2014 of $73.4 million ( $44.2 million net of tax) was frozen and reclassified into natural gas and crude oil and condensate revenues in the Statement of Operations throughout 2014 as the underlying hedged transactions occurred. As of December 31, 2014 , there are no gains or losses deferred in accumulated other comprehensive income (loss) associated with the Company’s commodity derivatives. As of December 31, 2015 , the Company did not have any outstanding commodity derivatives. In January 2016, the Company entered into natural gas swaps covering 52.0 Bcf of its expected natural gas production from April 2016 through October 2016 at a weighted-average price of $2.51 per Mcf. Effect of Derivative Instruments on the Consolidated Balance Sheet Fair Values of Derivative Instruments Derivative Assets Derivative Liabilities December 31, December 31, (In thousands) Balance Sheet Location 2015 2014 2015 2014 Derivatives Not Designated as Hedges Commodity contracts Derivative instruments (current assets) — 137,603 — — $ — $ 137,603 $ — $ — Offsetting of Derivative Assets and Liabilities in the Consolidated Balance Sheet December 31, (In thousands) 2015 2014 Derivative assets Gross amounts of recognized assets $ — $ 137,603 Gross amounts offset in the statement of financial position — — Net amounts of assets presented in the statement of financial position — 137,603 Gross amounts of financial instruments not offset in the statement of financial position — 2,338 Net amount $ — $ 139,941 Effect of Derivative Instruments on Accumulated Other Comprehensive Income (Loss) The effective portion of gain (loss) recognized in accumulated other comprehensive income (loss) on derivatives is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Commodity contracts $ — $ (133,310 ) $ (4,523 ) The effective portion of gain (loss) reclassified from accumulated other comprehensive income (loss) into income is as follows: Year Ended December 31, (In thousands) 2015 2014 (1) 2013 Natural gas revenues $ — $ (143,577 ) $ 52,733 Crude oil and condensate revenues — (626 ) 4,269 $ — $ (144,203 ) $ 57,002 (1) The Company ceased hedge accounting effective April 1, 2014. As a result, a loss of approximately $73.4 million related to amounts previously frozen in accumulated other comprehensive income (loss) was reclassified into income during 2014. Effect of Derivative Instruments on the Consolidated Statement of Operations Year Ended December 31, (In thousands) 2015 2014 2013 Derivatives Designated as Hedges Cash received (paid) on settlement of derivative instruments Natural gas $ — $ (70,557 ) $ 52,733 Crude oil and condensate — (218 ) 4,269 $ — $ (70,775 ) $ 57,002 Derivatives Not Designated as Hedges Cash received (paid) on settlement of derivative instruments Natural gas (1) $ — $ (73,020 ) $ — Crude oil and condensate (1) — (408 ) — Gain (loss) on derivative instruments 194,289 81,716 — Non-cash gain (loss) on derivative instruments Gain (loss) on derivative instruments (137,603 ) 137,603 — $ 56,686 $ 145,891 $ — $ 56,686 $ 75,116 $ 57,002 (1) Relates entirely to the reclassification from accumulated other comprehensive income (loss) of previously frozen losses associated with derivatives that were de-designated as cash flow hedges on April 1, 2014. There was no ineffectiveness recorded in the Company’s Consolidated Statement of Operations related to its derivative instruments designated as cash flow hedges for the years ended December 31, 2014 and 2013 , respectively. Additional Disclosures about Derivative Instruments and Hedging Activities The use of derivative instruments involves the risk that the counterparties will be unable to meet their obligations under the agreements. The Company's counterparties are primarily commercial banks and financial service institutions that management believes present minimal credit risk and its derivative contracts are with multiple counterparties to minimize its exposure to any individual counterparty. The Company performs both quantitative and qualitative assessments of these counterparties based on their credit ratings and credit default swap rates where applicable. Certain counterparties to the Company's derivative instruments are also lenders under its revolving credit facility. The Company's revolving credit facility and derivative instruments contain certain cross default and acceleration provisions that may require immediate payment of its derivative liabilities in certain situations. The Company also has netting arrangements with each of its counterparties that allow it to offset assets and liabilities from separate derivative contracts with that counterparty.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial Assets and Liabilities The following fair value hierarchy table presents information about the Company's financial assets and liabilities measured at fair value on a recurring basis: (In thousands) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at Assets Deferred compensation plan $ 12,921 $ — $ — $ 12,921 Total assets $ 12,921 $ — $ — $ 12,921 Liabilities Deferred compensation plan $ 22,371 $ — $ — $ 22,371 Total liabilities $ 22,371 $ — $ — $ 22,371 (In thousands) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at Assets Deferred compensation plan $ 13,115 $ — $ — $ 13,115 Derivative instruments — 51,645 85,958 137,603 Total assets $ 13,115 $ 51,645 $ 85,958 $ 150,718 Liabilities Deferred compensation plan $ 28,932 $ — $ — $ 28,932 Total liabilities $ 28,932 $ — $ — $ 28,932 The Company's investments associated with its deferred compensation plan consist of mutual funds and deferred shares of the Company's common stock that are publicly traded and for which market prices are readily available. The derivative instruments were measured based on quotes from the Company's counterparties. Such quotes have been derived using an income approach that considers various inputs including current market and contractual prices for the underlying instruments, quoted forward prices for natural gas and crude oil, basis differentials, volatility factors and interest rates, such as a LIBOR curve for a similar length of time as the derivative contract term as applicable. Estimates are verified using relevant NYMEX futures contracts and/or are compared to multiple quotes obtained from counterparties for reasonableness. The determination of the fair values presented above also incorporates a credit adjustment for non-performance risk. The Company measured the non-performance risk of its counterparties by reviewing credit default swap spreads for the various financial institutions with which it has derivative transactions while non-performance risk of the Company is evaluated using a market credit spread provided by the Company's bank. The Company has not incurred any losses related to non-performance risk of its counterparties and does not anticipate any material impact on its financial results due to non-performance by third parties. The most significant unobservable inputs relative to the Company's Level 3 derivative contracts are basis differentials and volatility factors. An increase (decrease) in these unobservable inputs would result in an increase (decrease) in fair value, respectively. The Company does not have access to the specific assumptions used in its counterparties' valuation models. Consequently, additional disclosures regarding significant Level 3 unobservable inputs were not provided. The following table sets forth a reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of period $ 85,958 $ (3,910 ) $ 41,159 Total gains (losses) (realized or unrealized): Included in earnings 32,864 35,067 52,733 Included in other comprehensive income — 3,755 (45,069 ) Settlements (118,822 ) 51,046 (52,733 ) Transfers in and/or out of level 3 — — — Balance at end of period $ — $ 85,958 $ (3,910 ) Change in unrealized gains (losses) relating to assets and liabilities still held at the end of the period $ — $ 85,958 $ — There were no transfers between Level 1 and Level 2 fair value measurements for the years ended December 31, 2015 , 2014 and 2013 . Non-Financial Assets and Liabilities The Company discloses or recognizes its non-financial assets and liabilities, such as impairments and acquisitions of oil and gas properties, at fair value on a nonrecurring basis. During the year ended December 31, 2014 , the Company acquired certain oil and gas properties that were allocated based on the relative fair value of the proved and unproved properties. The Company also recorded an impairment charge related to certain oil and gas properties during the years ended December 31, 2015 and 2014 . Refer to Note 2 for additional disclosures related to the non-recurring fair value measurements associated with these acquisitions and Note 3 for additional disclosures related to fair value associated with the impaired assets. As none of the Company’s other non-financial assets and liabilities were measured at fair value as of December 31, 2015 , 2014 and 2013 additional disclosures were not required. The estimated fair value of the Company's asset retirement obligation at inception is determined by utilizing the income approach by applying a credit-adjusted risk-free rate, which takes into account the Company's credit risk, the time value of money, and the current economic state to the undiscounted expected abandonment cash flows. Given the unobservable nature of the inputs, the measurement of the asset retirement obligations was classified as Level 3 in the fair value hierarchy. Fair Value of Other Financial Instruments The estimated fair value of financial instruments is the amount at which the instrument could be exchanged currently between willing parties. The carrying amount reported in the Consolidated Balance Sheet for cash and cash equivalents approximate fair value due to the short-term maturities of these instruments. Cash and cash equivalents are classified as Level 1 in the fair value hierarchy and the remaining financial instruments are classified as Level 2. The Company uses available market data and valuation methodologies to estimate the fair value of debt. The fair value of debt is the estimated amount the Company would have to pay a third party to assume the debt, including a credit spread for the difference between the issue rate and the period end market rate. The credit spread is the Company's default or repayment risk. The credit spread (premium or discount) is determined by comparing the Company's senior notes and revolving credit facility to new issuances (secured and unsecured) and secondary trades of similar size and credit statistics for both public and private debt. The fair value of all senior notes and the revolving credit facility is based on interest rates currently available to the Company. The Company's debt is valued using an income approach and classified as Level 3 in the fair value hierarchy. The carrying amount and fair value of debt is as follows : December 31, 2015 December 31, 2014 (In thousands) Carrying Amount Estimated Fair Value Carrying Estimated Fair Value Debt $ 2,025,000 $ 1,848,391 $ 1,752,000 $ 1,850,867 Current maturities (20,000 ) (20,378 ) — — Long-term debt, excluding current maturities $ 2,005,000 $ 1,828,013 $ 1,752,000 $ 1,850,867

Asset Retirement Obligation

Asset Retirement Obligation	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	Asset Retirement Obligations Activity related to the Company's asset retirement obligations is as follows: (In thousands) Year Ended Balance at beginning of period $ 126,655 Liabilities incurred 12,235 Liabilities settled (175 ) Accretion expense 6,891 Balance at end of period $ 145,606 As of December 31, 2015 and 2014 , approximately $2.0 million is included in accrued liabilities in the Consolidated Balance Sheet, which represents the current portion of the Company’s asset retirement obligation.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Transportation and Gathering Agreements The Company has entered into certain natural gas, oil and NGL transportation and gathering agreements with various pipeline carriers. Under certain of these agreements, the Company is obligated to transport minimum daily quantities, or pay for any deficiencies at a specified rate. The Company is also obligated under certain of these arrangements to pay a demand charge for firm capacity rights on pipeline systems regardless of the amount of pipeline capacity utilized by the Company. In most cases, the Company's production commitment to these pipelines is expected to exceed minimum daily quantities provided in the agreements. If the Company does not utilize the capacity, it can release it to others, thus reducing its potential liability. As of December 31, 2015 , the Company's future minimum obligations under transportation and gathering agreements are as follows: (In thousands) 2016 $ 136,468 2017 178,699 2018 151,233 2019 139,387 2020 133,960 Thereafter 1,188,906 $ 1,928,653 Drilling Rig Commitments As of December 31, 2015 , the Company has remaining commitments for two drilling rigs for its capital program in the Marcellus Shale and Eagle Ford Shale with initial terms ranging from two to three years. As of December 31, 2015 , the future minimum commitments under these agreements are $7.7 million in 2016 . Lease Commitments The Company leases certain office space, warehouse facilities, vehicles, machinery and equipment under cancelable and non-cancelable leases. Rent expense under these arrangements totaled $13.9 million , $10.8 million and $12.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. Future minimum rental commitments under non-cancelable leases in effect at December 31, 2015 are as follows: (In thousands) 2016 $ 7,471 2017 7,036 2018 6,549 2019 6,224 2020 5,834 Thereafter 10,976 $ 44,090 Legal Matters The Company is a defendant in various other legal proceedings arising in the normal course of business. All known liabilities are accrued when management determines they are probable based on its best estimate of the potential loss. While the outcome and impact of these legal proceedings on the Company cannot be predicted with certainty, management believes that the resolution of these proceedings will not have a material effect on the Company's financial position, results of operations or cash flows. Contingency Reserves When deemed necessary, the Company establishes reserves for certain legal proceedings. The establishment of a reserve is based on an estimation process that includes the advice of legal counsel and subjective judgment of management. While management believes these reserves to be adequate, it is reasonably possible that the Company could incur additional losses with respect to those matters in which reserves have been established. The Company believes that any such amount above the amounts accrued would not be material to the Consolidated Financial Statements. Future changes in facts and circumstances not currently foreseeable could result in the actual liability exceeding the estimated ranges of loss and amounts accrued.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense (benefit) is summarized as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Current Federal $ 983 $ 44,887 $ 56,544 State (1,397 ) (4,387 ) 10,841 (414 ) 40,500 67,385 Deferred Federal (72,869 ) (32,375 ) 111,147 State (99 ) (80,192 ) 27,233 (72,968 ) (112,567 ) 138,380 Income tax expense (benefit) $ (73,382 ) $ (72,067 ) $ 205,765 Income tax expense (benefit) was different than the amounts computed by applying the statutory federal income tax rate as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Statutory federal income tax rate 35 % 35 % 35 % Computed "expected" federal income tax $ (65,546 ) $ 11,341 $ 169,938 State income tax, net of federal income tax benefit (3,152 ) 903 17,513 Deferred tax adjustment related to change in overall state tax rate 2,822 (86,956 ) 15,220 Valuation allowance 187 3,977 — Uncertain tax positions — (1,974 ) 2,400 Provision to return adjustments (6,326 ) (791 ) 700 Other, net (1,367 ) 1,433 (6 ) Income tax expense (benefit) $ (73,382 ) $ (72,067 ) $ 205,765 The composition of deferred tax liabilities and deferred tax assets were as follows: December 31, (In thousands) 2015 2014 Deferred Tax Assets Net operating losses $ 223,402 $ 141,961 Alternative minimum tax credits 228,693 227,719 Foreign tax credits 3,837 4,525 Incentive compensation 22,509 21,961 Deferred compensation 7,869 9,531 Post-retirement benefits 13,556 13,689 Other 2,905 5,526 Less valuation allowance (4,965 ) (4,779 ) Total 497,806 420,133 Deferred Tax Liabilities Properties and equipment 1,303,840 1,248,532 Equity method investments 1,202 — Derivative instruments — 50,750 Total 1,305,042 1,299,282 Net deferred tax liabilities $ 807,236 $ 879,149 As of December 31, 2015 , the Company had alternative minimum tax credit carryforwards of $228.7 million , which do not expire and can be used to offset regular income taxes in future years to the extent that regular income taxes exceed the alternative minimum tax in any such year. The Company also had net operating loss carryforwards of $685.3 million and $530.4 million for federal and state reporting purposes, respectively, the majority of which will expire between 2021 and 2035. The Company has $4.6 million of state valuation allowances, and believes it is more likely than not that the remainder of the deferred tax benefits will be realized prior to their expiration. Tax benefits related to employee stock-based compensation included in net operating loss carryforwards but not reflected in deferred tax assets as of December 31, 2015 are approximately $117.8 million . For state income tax purposes, the Company must estimate the respective amounts of future earnings that are subject to income tax in the various states in which the Company operates. These estimates may change based on a variety of factors, including, but not limited to, the composition and location of the Company’s asset base, its employees, and its customers. In 2015 , the Company’s overall effective tax rate increase d compared to 2014 . The overall effective tax rate was significantly lower in 2014 due to a change in the effective state income tax rate based on updated state apportionment factors in the states in which the Company operates. The 2014 decrease in the Company’s state apportionment factors was primarily driven by a shift in the sourcing of revenues based on the location of customers to whom the Company ultimately sells its natural gas in the northeast United States. The 2014 decrease in the effective state income tax rate significantly affected the Company’s estimated net state deferred tax liabilities reflected in its Consolidated Balance Sheet, resulting in an income tax benefit of approximately $87.0 million that was reflected in the Company’s provision for income taxes in 2014 . Unrecognized Tax Benefits A reconciliation of unrecognized tax benefits is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of year $ 663 $ 3,700 $ — Additions based on tax provisions related to the current year — — 3,700 Additions for tax positions of prior years — — — Reductions for tax positions of prior years — (3,037 ) — Settlements — — — Balance at end of year $ 663 $ 663 $ 3,700 During 2013, the Company recorded unrecognized tax benefits of $3.7 million based on the allocation of certain gains associated with its divestitures for purposes of computing state income taxes. These benefits were reduced during 2014 by $3.0 million based on changes to the Company's state tax rates. There was no change to the Company's unrecognized tax benefits during 2015. If recognized, the net tax benefit of $0.7 million would not have a material effect on the Company's effective tax rate. The Company files income tax returns in the U.S. federal, various states and other jurisdictions. The Company is no longer subject to examinations by state authorities before 2011 or by federal authorities before 2012. The Company is currently under examination by the Internal Revenue Service for its 2012 tax year. The Company believes that appropriate provisions have been made for all jurisdictions and all open years, and that any assessment on these filings will not have a material impact on the Company's financial position, results of operations or cash flows.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans Postretirement Benefits The Company provides certain health care benefits for retired employees, including their spouses, eligible dependents and surviving spouses (retirees). These benefits are commonly called postretirement benefits. The health care plans are contributory, with participants' contributions adjusted annually. Most employees become eligible for these benefits if they meet certain age and service requirements at retirement. The Company was providing postretirement benefits to 276 retirees and their dependents at the end of 2015 and 278 retirees and their dependents at the end of 2014 . Obligations and Funded Status The funded status represents the difference between the accumulated benefit obligation of the Company's postretirement plan and the fair value of plan assets at December 31. The postretirement plan does not have any plan assets; therefore, the unfunded status is equal to the amount of the December 31 accumulated benefit obligation. The change in the Company's postretirement benefit obligation is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Change in Benefit Obligation Benefit obligation at beginning of year $ 37,076 $ 34,995 $ 40,168 Service cost 1,808 1,295 1,739 Interest cost 1,448 1,343 1,500 Actuarial (gain) loss (2,829 ) 373 (7,618 ) Benefits paid (877 ) (930 ) (794 ) Benefit obligation at end of year $ 36,626 $ 37,076 $ 34,995 Change in Plan Assets Fair value of plan assets at end of year — — — Funded status at end of year $ (36,626 ) $ (37,076 ) $ (34,995 ) Amounts Recognized in the Balance Sheet Amounts recognized in the balance sheet consist of the following: December 31, (In thousands) 2015 2014 2013 Current liabilities $ 1,333 $ 1,249 $ 1,441 Long-term liabilities 35,293 35,827 33,554 $ 36,626 $ 37,076 $ 34,995 Amounts Recognized in Accumulated Other Comprehensive Income (Loss) Amounts recognized in accumulated other comprehensive income (loss) consist of the following: December 31, (In thousands) 2015 2014 2013 Net actuarial loss $ 580 $ 3,408 $ 3,010 $ 580 $ 3,408 $ 3,010 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income (Loss) Year Ended December 31, (In thousands) 2015 2014 2013 Components of Net Periodic Postretirement Benefit Cost Service cost $ 1,808 $ 1,295 $ 1,739 Interest cost 1,448 1,343 1,500 Amortization of net loss — (26 ) 641 Net periodic postretirement cost $ 3,256 $ 2,612 $ 3,880 Other Changes in Benefit Obligations Recognized in Other Comprehensive Income (Loss) Net gain (loss) $ (2,829 ) $ 373 $ (7,618 ) Amortization of net (gain) loss — 26 (641 ) Total recognized in other comprehensive income (2,829 ) 399 (8,259 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 427 $ 3,011 $ (4,379 ) Assumptions Assumptions used to determine projected postretirement benefit obligations and postretirement costs are as follows: December 31, 2015 2014 2013 Discount rate (1) 4.25 % 4.00 % 4.75 % Health care cost trend rate for medical benefits assumed for next year 5.50 % 6.00 % 6.50 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.50 % 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate 2018 2018 2018 _______________________________________________________________________________ (1) Represents the year end rates used to determine the projected benefit obligation. To compute postretirement cost in 2015 , 2014 and 2013 , respectively, the beginning of year discount rates of 4.00% , 4.75% and 4.00% were used. Coverage provided to participants age 65 and older is under a fully-insured arrangement. The Company subsidy is limited to 60% of the expected annual fully-insured premium for participants age 65 and older. For all participants under age 65, the Company subsidy for all retiree medical and prescription drug benefits, beginning January 1, 2006, was limited to an aggregate annual amount not to exceed $648,000 . This limit increases by 3.5% annually thereafter. Assumed health care cost trend rates may have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects: (In thousands) 1-Percentage-Point Increase 1-Percentage-Point Decrease Effect on total of service and interest cost $ 618 $ (539 ) Effect on postretirement benefit obligation 5,849 (4,718 ) Cash Flows Contributions. The Company expects to contribute approximately $1.4 million to the postretirement benefit plan in 2016 . Estimated Future Benefit Payments. The following estimated benefit payments under the Company's postretirement plans, which reflect expected future service, are expected to be paid as follows: (In thousands) 2016 1,361 2017 1,430 2018 1,551 2019 1,718 2020 1,875 Years 2021 - 2025 11,404 Savings Investment Plan The Company has a Savings Investment Plan (SIP), which is a defined contribution plan. The Company matches a portion of employees' contributions in cash. Participation in the SIP is voluntary and all regular employees of the Company are eligible to participate. The Company matches employee contributions dollar-for-dollar, up to the maximum IRS limit, on the first six percent of an employee's pretax earnings. The SIP also provides for discretionary profit sharing contributions in an amount equal to nine percent of an eligible plan participant's salary and bonus. During the years ended December 31, 2015 , 2014 and 2013 , the Company made contributions of $7.1 million , $7.2 million and $6.9 million , respectively, which are included in general and administrative expense in the Consolidated Statement of Operations. The Company's common stock is an investment option within the SIP. Deferred Compensation Plan The Company has a deferred compensation plan which is available to officers and certain members of the Company's management group and acts as a supplement to the SIP. The Internal Revenue Code does not cap the amount of compensation that may be taken into account for purposes of determining contributions to the deferred compensation plan and does not impose limitations on the amount of contributions to the deferred compensation plan. At the present time, the Company anticipates making a contribution to the deferred compensation plan on behalf of a participant in the event that Internal Revenue Code limitations cause a participant to receive less than the Company matching contribution under the SIP. The assets of the deferred compensation plan are held in a rabbi trust and are subject to additional risk of loss in the event of bankruptcy or insolvency of the Company. Under the deferred compensation plan, the participants direct the deemed investment of amounts credited to their accounts. The trust assets are invested in either mutual funds that cover the investment spectrum from equity to money market, or may include holdings of the Company's common stock, which is funded by the issuance of shares to the trust. The mutual funds are publicly traded and have market prices that are readily available. The Company's common stock is not currently an investment option in the deferred compensation plan. Shares of the Company's stock currently held in the deferred compensation plan represent vested performance share awards that were previously deferred into the rabbi trust. Settlement payments are made to participants in cash, either in a lump sum or in periodic installments. The market value of the trust assets, excluding the Company's common stock, was $12.9 million and $13.1 million at December 31, 2015 and 2014 , respectively, and is included in other assets in the Consolidated Balance Sheet. Related liabilities, including the Company's common stock, totaled $22.4 million and $28.9 million at December 31, 2015 and 2014 , respectively, and are included in other liabilities in the Consolidated Balance Sheet. With the exception of the Company's common stock, there is no impact on earnings or earnings per share from the changes in market value of the deferred compensation plan assets because the changes in market value of the trust assets are offset completely by changes in the value of the liability, which represents trust assets belonging to plan participants. As of December 31, 2015 and 2014 , 534,174 shares of the Company's common stock were held in the rabbi trust. These shares were recorded at the market value on the date of deferral, which totaled $5.7 million at December 31, 2015 and 2014 , respectively, and is included in additional paid-in capital in stockholders' equity in the Consolidated Balance Sheet. The Company recognized compensation expense (benefit) of $(6.4) million , $(4.9) million and $7.4 million in 2015 , 2014 and 2013 , respectively, which is included in general and administrative expense in the Consolidated Statement of Operations representing the increase (decrease) in the closing price of the Company's shares held in the trust. The Company's common stock issued to the trust is not considered outstanding for purposes of calculating basic earnings per share, but is considered a common stock equivalent in the calculation of diluted earnings per share. The Company made contributions to the deferred compensation plan of $1.0 million , $0.8 million and $0.7 million in 2015 , 2014 and 2013 , respectively, which are included in general and administrative expense in the Consolidated Statement of Operations.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Capital Stock	Capital Stock Incentive Plans On May 1, 2014, the Company’s shareholders approved the 2014 Incentive Plan, which replaced the 2004 Incentive Plan that expired on April 29, 2014. Under the 2014 Incentive Plan, incentive and non-statutory stock options, stock appreciation rights (SARs), stock awards, cash awards and performance awards may be granted to key employees, consultants and officers of the Company. Non-employee directors of the Company may be granted discretionary awards under the 2014 Incentive Plan consisting of stock options or stock awards. A total of 18 million shares of common stock may be issued under the 2014 Incentive Plan. Under the 2014 Incentive Plan, no more than 10 million shares may be issued pursuant to incentive stock options. No additional awards may be granted under the 2014 Incentive Plan on or after May 1, 2024. At December 31, 2015 , approximately 17.1 million shares are available for issuance under the 2014 Incentive Plan. No additional awards will be granted under any of the Company’s prior plans, including the 2004 Incentive Plan. Awards outstanding under the 2004 Incentive Plan will remain outstanding in accordance with their original terms and conditions. Treasury Stock In August 1998, the Board of Directors authorized a share repurchase program under which the Company may purchase shares of common stock in the open market or in negotiated transactions. The timing and amount of these stock purchases are determined at the discretion of management. The Company may use the repurchased shares to fund stock compensation programs presently in existence, or for other corporate purposes. All purchases executed to date have been through open market transactions. There is no expiration date associated with the authorization to repurchase shares of the Company. During 2015, there were no share repurchases. During the year ended December 31, 2014 and 2013 , the Company repurchased 4.3 million shares for a total cost of $138.9 million and 4.8 million shares for a total cost of $164.6 million , respectively. Since the authorization date, the Company has repurchased 29.9 million shares of the 40.0 million total shares authorized, of which 20.0 million shares have been retired, for a total cost of approximately $388.4 million . No treasury shares have been delivered or sold by the Company subsequent to the repurchase. As of December 31, 2015 , 9.9 million shares were held as treasury stock. Dividend Restrictions The Board of Directors of the Company determines the amount of future cash dividends, if any, to be declared and paid on the common stock depending on, among other things, the Company's financial condition, funds from operations, the level of its capital and exploration expenditures, and its future business prospects. None of the senior note or credit agreements in place have restricted payment provisions or other provisions limiting dividends.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation General Stock-based compensation expense for the years ended December 31, 2015 , 2014 and 2013 was $13.7 million , $21.5 million and $51.8 million , respectively, and is included in general and administrative expense in the Consolidated Statement of Operations. For the years ended December 31, 2014 and 2013 , the Company realized $(1.4) million and $18.9 million tax (expense) benefit related to the federal tax deduction in excess of book compensation cost for employee stock-based compensation. There was no tax benefit recognized from stock-based compensation during the year ended December 31, 2015 . The Company is able to recognize tax benefits only to the extent they reduce the Company's income taxes payable. Restricted Stock Awards Restricted stock awards are granted from time to time to employees of the Company. The fair value of restricted stock grants under the 2014 Incentive Plan is based on the closing stock price on the grant date. Restricted stock awards generally vest either at the end of a three year service period or on a graded or graduated vesting basis at each anniversary date over a three or four year service period. For awards that vest at the end of the service period, expense is recognized ratably using a straight-line approach over the service period. Under the graded or graduated approach, the Company recognizes compensation cost ratably over the requisite service period, as applicable, for each separately vesting tranche as though the awards are, in substance, multiple awards. For all restricted stock awards, vesting is dependent upon the employees' continued service with the Company, with the exception of employment termination due to death, disability or retirement. The Company accelerates the vesting period for retirement-eligible employees for purposes of recognizing compensation expense in accordance with the vesting provisions of the Company's stock-based compensation programs. The Company used an annual forfeiture rate assumption ranging from 5.0% to 6.0% for purposes of recognizing stock-based compensation expense for restricted stock awards. The annual forfeiture rates were based on the Company's actual forfeiture history for this type of award to various employee groups. The following table is a summary of restricted stock award activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 49,869 $ 33.40 27,806 $ 20.53 71,508 $ 11.82 Granted 5,900 25.44 47,500 34.76 7,200 35.70 Vested (5,944 ) 22.55 (17,437 ) 15.84 (50,902 ) 10.44 Forfeited — — (8,000 ) 35.00 — — Outstanding at end of period (1)(2) 49,825 $ 33.76 49,869 $ 33.40 27,806 $ 20.53 _______________________________________________________________________________ (1) As of December 31, 2015 , the aggregate intrinsic value was $0.9 million and was calculated by multiplying the closing market price of the Company's stock on December 31, 2015 by the number of non-vested restricted stock awards outstanding. (2) As of December 31, 2015 , the weighted average remaining contractual term of non-vested restricted stock awards outstanding was 1.2 years . Compensation expense recorded for all restricted stock awards for the years ended December 31, 2015 , 2014 and 2013 was $0.4 million , $1.0 million and $0.2 million , respectively. Unamortized expense as of December 31, 2015 for all outstanding restricted stock awards was $0.5 million and will be recognized over the next year. The total fair value of restricted stock awards that vested during 2015 , 2014 and 2013 was $0.2 million , $0.6 million and $1.6 million , respectively. Restricted Stock Units Restricted stock units are granted from time to time to non-employee directors of the Company. The fair value of the restricted stock units under the 2014 Incentive Plan is based on the closing stock price on the grant date. These units vest immediately and compensation expense is recorded immediately. Restricted stock units are issued when the director ceases to be a director of the Company. The following table is a summary of restricted stock unit activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 604,214 $ 12.48 566,321 $ 10.75 515,468 $ 9.10 Granted and fully vested 51,292 27.87 37,893 38.28 50,853 27.53 Issued (230,068 ) 13.45 — — — — Forfeited — — — — — — Outstanding at end of period (1)(2) 425,438 $ 13.81 604,214 $ 12.48 566,321 $ 10.75 _______________________________________________________________________________ (1) As of December 31, 2015 , the aggregate intrinsic value was $7.5 million and was calculated by multiplying the closing market price of the Company's stock on December 31, 2015 by the number of outstanding restricted stock units. (2) Due to the immediate vesting of the units and the unknown term of each director, the weighted-average remaining contractual term in years has not been provided. Compensation expense recorded for all restricted stock units for the years ended December 31, 2015 , 2014 and 2013 was $1.4 million , $1.5 million and $1.4 million , respectively, which reflects the total fair value of these units. Stock Appreciation Rights Stock appreciation rights (SARs) allow the employee to receive any intrinsic value over the grant date market price that may result from the price appreciation of the common shares granted. All of these awards have graded-vesting features and vest over a service period of three years , with one-third of the award becoming exercisable each year on the anniversary date of the grant and have a contractual term of seven years . The following table is a summary of SAR activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Outstanding at beginning of period 667,764 $ 12.63 667,764 $ 12.63 1,722,444 $ 9.75 Granted — — — — — — Exercised (109,218 ) 13.19 — — (1,054,680 ) 7.92 Forfeited or expired — — — — — — Outstanding at end of period (1) 558,546 $ 12.52 667,764 $ 12.63 667,764 $ 12.63 Exercisable at end of period (2) 558,546 $ 12.52 590,960 $ 11.98 386,582 $ 11.33 _______________________________________________________________________________ (1) The intrinsic value of a SAR is the amount which the current market value of the underlying stock exceeds the exercise price of the SAR. As of December 31, 2015 , the aggregate intrinsic value and weighted-average remaining contractual term of SARs outstanding was $2.9 million and 2.2 years , respectively. (2) As of December 31, 2015 , the aggregate intrinsic value and weighted-average remaining contractual term of SARs exercisable was $2.9 million and 2.2 years , respectively. Compensation expense recorded for all outstanding SARs for the years ended December 31, 2014 and 2013 was $0.1 million and $0.3 million , respectively. As of December 31, 2014 , there was no remaining unamortized expense to be recognized for the outstanding SARs. The expected term was derived by reviewing minimum and maximum expected term outputs from the Black-Scholes model based on award type and employee type. This term represents the period of time that awards granted are expected to be outstanding. The stock price volatility was calculated using historical closing stock price data for the Company for the period associated with the expected term through the grant date of each award. The risk free rate of return percentages are based on the continuously compounded equivalent of the U.S. Treasury (Nominal 10) within the expected term as measured on the grant date. The expected dividend percentage assumes that the Company will continue to pay a consistent level of dividend each quarter. Performance Share Awards The Company grants three types of performance share awards: two based on performance conditions measured against the Company's internal performance metrics (Employee Performance Share Awards and Hybrid Performance Share Awards) and one based on market conditions measured based on the Company's performance relative to a predetermined peer group (TSR Performance Share Awards). The performance period for these awards commences on January 1 of the respective year in which the award was granted and extends over a three -year performance period. For all performance share awards, the Company used an annual forfeiture rate assumption ranging from 0% to 6% for purposes of recognizing stock-based compensation expense for its performance share awards. Performance Share Awards Based on Internal Performance Metrics The fair value of performance award grants based on internal performance metrics is based on the closing stock price on the grant date. Each performance award represents the right to receive up to 100% of the award in shares of common stock. Employee Performance Share Awards. The Employee Performance Share Awards vest at the end of the three -year performance period. An employee will earn one-third of the award for each of the three performance metrics that the Company meets . These performance metrics are set by the Company's Compensation Committee and are based on the Company's average production, average finding costs and average reserve replacement over a three -year performance period. Based on the Company's probability assessment at December 31, 2015 , it is considered probable that all of the criteria for these awards will be met. The following table is a summary of activity for Employee Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 1,088,960 $ 25.18 1,657,980 $ 16.25 1,919,640 $ 12.27 Granted 349,780 27.71 241,130 39.43 379,540 26.62 Issued and fully vested (504,620 ) 17.59 (751,780 ) 10.19 (610,960 ) 10.13 Forfeited (8,530 ) 31.11 (58,370 ) 23.57 (30,240 ) 17.06 Outstanding at end of period 925,590 $ 30.23 1,088,960 $ 25.18 1,657,980 $ 16.25 Hybrid Performance Share Awards. The Hybrid Performance Share Awards have a three -year graded performance period. The awards vest 25% on each of the first and second anniversary dates and 50% on the third anniversary provided that the Company has $100 million or more of operating cash flow for the year preceding the vesting date, as set by the Company's Compensation Committee. If the Company does not meet the performance metric for the applicable period, then the portion of the performance shares that would have been issued on that anniversary date will be forfeited. Based on the Company's probability assessment at December 31, 2015 , it is considered probable that the criteria for these awards will be met. The following table is a summary of activity for the Hybrid Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 329,061 $ 29.27 450,212 $ 18.96 592,162 $ 13.11 Granted 194,947 27.71 123,257 39.43 169,980 26.62 Issued and fully vested (151,623 ) 24.56 (244,408 ) 15.41 (311,930 ) 12.03 Forfeited — — — — — — Outstanding at end of period 372,385 $ 30.37 329,061 $ 29.27 450,212 $ 18.96 Performance Share Awards Based on Market Conditions These awards have both an equity and liability component, with the right to receive up to the first 100% of the award in shares of common stock and the right to receive up to an additional 100% of the value of the award in excess of the equity component in cash. The equity portion of these awards is valued on the grant date and is not marked to market, while the liability portion of the awards is valued as of the end of each reporting period on a mark-to-market basis. The Company calculates the fair value of the equity and liability portions of the awards using a Monte Carlo simulation model. TSR Performance Share Awards. The TSR Performance Share Awards granted are earned, or not earned, based on the comparative performance of the Company's common stock measured against a predetermined group of companies in the Company's peer group over a three -year performance period. The following table is a summary of activity for the TSR Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share (1) Shares Weighted- Average Grant Date Fair Value per Share (1) Shares Weighted- Average Grant Date Fair Value per Share (1) Outstanding at beginning of period 674,787 $ 22.42 860,686 $ 14.06 605,706 $ 10.27 Granted 292,421 19.29 184,885 32.04 254,980 23.06 Issued and fully vested (234,922 ) 14.16 (370,784 ) 7.81 — — Forfeited — — — — — — Outstanding at end of period 732,286 $ 23.82 674,787 $ 22.42 860,686 $ 14.06 _______________________________________________________________________________ (1) The grant date fair value figures in this table represent the fair value of the equity component of the performance share awards. The current portion of the liability, included in accrued liabilities in the Consolidated Balance Sheet at December 31, 2015 and 2014 was $1.8 million and $7.0 million , respectively. The non-current portion of the liability for the TSR Performance Share Awards, included in other liabilities in the Consolidated Balance Sheet at December 31, 2015 and 2014 , was $0.9 million and $4.0 million , respectively. The Company made cash payments during the years ended December 31, 2015 and 2014 of $7.0 million and $14.3 million , respectively. There were no cash payouts during 2013 associated with the TSR Performance Share Awards. The following assumptions were used to determine the grant date fair value of the equity component of the TSR Performance Share Awards for the respective periods: Year Ended December 31, 2015 2014 2013 Fair value per performance share award granted during the period $ 19.29 $ 32.04 $ 23.06 Assumptions Stock price volatility 32.3 % 41.3 % 43.8 % Risk free rate of return 1.0 % 0.7 % 0.4 % Expected dividend yield 0.3 % 0.2 % 0.2 % The following assumptions were used to determine the fair value of the liability component of the TSR Performance Share Awards for the respective periods: December 31, 2015 2014 2013 Fair value per performance share award at the end of the period $2.49 - $6.39 $12.88 - $29.72 $23.96 - $38.61 Assumptions Stock price volatility 33.5% - 37.5% 29.1% - 29.7% 30.2% - 35.9% Risk free rate of return 0.7% - 1.1% 0.3% - 0.7% 0.1% - 0.4% Expected dividend yield —% 0.3% 0.2% The stock price volatility was calculated using historical closing stock price data for the Company for the period associated with the expected term through the grant date of each award. The risk free rate of return percentages are based on the continuously compounded equivalent of the U.S. Treasury (Nominal 10) within the expected term as measured on the grant date. The expected dividend percentage assumes that the Company will continue to pay a consistent level of dividend each quarter. Other Information Compensation expense recorded for both the equity and liability components of all performance share awards for the years ended December 31, 2015 , 2014 and 2013 was $18.3 million , $20.8 million and $30.9 million , respectively. Total unamortized compensation expense related to the equity component of performance shares at December 31, 2015 was $18.4 million and will be recognized over the next 1.0 years . As of December 31, 2015 , the aggregate intrinsic value for all performance share awards was $35.9 million and was calculated by multiplying the closing market price of the Company's stock on December 31, 2015 by the number of unvested performance share awards outstanding. As of December 31, 2015 , the weighted average remaining contractual term of unvested performance share awards outstanding was approximately 1.1 years . On December 31, 2015 , the performance period ended for two types of performance share awards that were granted in 2013 . For the Employee Performance Share Awards, the calculation of the three -year average of the three internal performance metrics was completed in the first quarter of 2016 and was certified by the Compensation Committee in February 2016 . As the Company achieved the three performance metrics, 340,960 shares with a grant date fair value of $9.1 million were issued in February 2016 . For the TSR Performance Share Awards, 254,980 shares with a grant date fair value of $5.9 million were issued, in addition to a cash payment of $1.8 million , based on the Company's ranking relative to a predetermined peer group. The calculation of the award payout was certified by the Compensation Committee on January 5, 2016 . Supplemental Employee Incentive Plan The Supplemental Employee Incentive Plan (the Plan) adopted by the Company's Board of Directors is intended to provide a compensation tool tied to stock market value creation to serve as an incentive and retention vehicle for full-time, non-officer employees by providing for cash payments in the event the Company's common stock reaches a specified trading price. The Compensation Committee can increase any of the payments as applied to any employee if desired. Any deferred portion will only be paid if the participant is employed by the Company, or has terminated employment by reason of retirement, death or disability (as provided in the Plan). Payments are subject to certain other restrictions contained in the Plan. The Plan currently provides for a payout if the closing price per share of the Company's common stock for any 20 trading days out of any 60 days consecutive trading days equals or exceeds an interim price goal per share within two years of the effective date of the plan (interim trigger date) or a final price goal per share within four years of the effective date of the plan (final trigger date). Under the Plan and upon approval by the Compensation Committee, each eligible employee may receive a distribution of 20% of base salary if the interim trigger is met or 50% of base salary if the final trigger is met (or an incremental 30% of base salary if the interim trigger was previously achieved). In accordance with the Plan, in the event either the interim or final trigger date occurs within the first 30 months from the effective date, 25% of the total distribution will be paid immediately and the remaining 75% will be deferred and paid at a future date as described in the Plan. For final trigger dates occurring during the last 18 months but before the end of the Plan, total distribution will be paid immediately. The Plan is accounted for as a liability award under the authoritative accounting guidance for stock-based compensation and is valued as of the end of each reporting period on a mark-to-market basis using a Monte Carlo simulation model. In addition to the expected value of plan payouts, the simulation technique also generates an expected trigger date for the two types of payments made under this plan, which is used to determine the requisite service period. The Company recognized compensation expense (benefit) of $(0.3) million , $3.0 million and $11.5 million for years ended December 31, 2015 , 2014 and 2013 , respectively, related to the Plan. The Company made payments of $13.0 million under the Plan for year ended December 31, 2014 . SEIP III. On May 1, 2012, the Company's Board of Directors adopted the Supplemental Employee Incentive Plan III (SEIP III) to replace the Supplemental Employee Incentive Plan II with an effective date of July 1, 2013. The SEIP III provided for a payout under the Plan if the closing price per share of the Company's common stock equals or exceeds the price goal of $25.00 per share by June 30, 2014 (interim trigger date) or $37.50 per share by June 30, 2016 (final trigger date). On February 11, 2013, the Company achieved the price goal of $25.00 per share prior to the interim trigger date. Accordingly, a total distribution of approximately $6.8 million was earned by the Company's eligible employees under the Plan, of which 25% of the total distribution, or $1.7 million , was paid in February 2013 and the remaining 75% , or $4.9 million , was paid in August 2014 in accordance with the SEIP III. On August 27, 2013, the Company achieved the price goal of $37.50 per share prior to the final trigger date. Accordingly, a total distribution of approximately $11.1 million was earned by the Company's eligible employees under the Plan, of which 25% of the total distribution, or $2.8 million , was paid in September 2013 and the remaining 75% , or $8.1 million , was paid in August 2014 in accordance with the SEIP III. SEIP IV. On September 19, 2013, the Company's Board of Directors adopted the Supplemental Employee Incentive Plan IV (SEIP IV) to replace the SEIP III with an effective date of October 1, 2013. The SEIP IV provides for a payout under the Plan if the closing price per share of the Company's common stock equals or exceeds the price goal of $55.00 per share by September 30, 2015 (interim trigger date) or $80.00 per share by September 30, 2017 (final trigger date). There were no amounts paid with respect to the interim trigger date as the Company's common stock did not equal or exceed the respective interim price goal of $55.00 per share. The following assumptions were used to determine the fair value of the SEIP IV liabilities at the end of the respective periods: December 31, 2015 2014 2013 Valuation Assumptions Stock price volatility 33.9 % 33.4 % 38.0 % Risk free rate of return 1.0 % 1.0 % 1.1 % Annual salary increase rate 4.0 % 4.0 % 4.0 % Annual turnover rate 4.6 % 4.6 % 4.6 % Deferred Performance Shares As of December 31, 2015 , 534,174 shares of the Company's common stock representing vested performance share awards were deferred into the deferred compensation plan. No shares were sold out of the plan in 2015 . During 2015 , a decrease to the deferred compensation liability of $(6.4) million was recognized, which represents the decrease in the closing price of the Company's shares held in the trust during the period. The decrease in compensation expense was included in general and administrative expense in the Consolidated Statement of Operations.

Earnings per Common Share

Earnings per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings per Common Share	Earnings per Common Share Basic earnings per share (EPS) is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted EPS is similarly calculated except that the common shares outstanding for the period is increased using the treasury stock method to reflect the potential dilution that could occur if outstanding stock appreciation rights were exercised and stock awards were vested at the end of the applicable period. The following is a calculation of basic and diluted weighted-average shares outstanding: December 31, (In thousands) 2015 2014 2013 Weighted-average shares - basic 413,696 415,840 420,188 Dilution effect of stock appreciation rights and stock awards at end of period — 1,761 2,187 Weighted-average shares - diluted 413,696 417,601 422,375 Weighted-average shares excluded from diluted EPS due to the anti-dilutive effect 1,481 20 5

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss) by component, net of tax, were as follows: (In thousands) Net Gains (Losses) on Cash Flow Hedges Postretirement Benefits Total Balance at December 31, 2012 $ 30,717 $ (6,837 ) $ 23,880 Other comprehensive income (loss) before reclassifications (2,720 ) 4,641 1,921 Amounts reclassified from accumulated other comprehensive income (loss) (34,548 ) 386 (34,162 ) Net current-period other comprehensive income (loss) $ (37,268 ) $ 5,027 $ (32,241 ) Balance at December 31, 2013 $ (6,551 ) $ (1,810 ) $ (8,361 ) Other comprehensive income (loss) before reclassifications (80,175 ) (325 ) (80,500 ) Amounts reclassified from accumulated other comprehensive income (loss) 86,726 (16 ) 86,710 Net current-period other comprehensive income (loss) 6,551 (341 ) 6,210 Balance at December 31, 2014 $ — $ (2,151 ) $ (2,151 ) Other comprehensive income (loss) before reclassifications — 1,786 1,786 Amounts reclassified from accumulated other comprehensive income (loss) — — — Net current-period other comprehensive income (loss) — 1,786 1,786 Balance at December 31, 2015 $ — $ (365 ) $ (365 ) Amounts reclassified from accumulated other comprehensive income (loss) into the Consolidated Statement of Operations were as follows: Year Ended December 31, Affected Line Item in the Condensed Consolidated Statement of Operations (In thousands) 2015 2014 2013 Net gains (losses) on cash flow hedges Commodity contracts $ — $ (143,577 ) $ 52,733 Natural gas revenues Commodity contracts — (626 ) 4,269 Crude oil and condensate revenues Postretirement benefits Amortization of net (gain) loss — 26 (641 ) General and administrative expense — (144,177 ) 56,361 Total before tax — 57,467 (22,199 ) Tax expense Total reclassifications for the period $ — $ (86,710 ) $ 34,162 Net of tax

Additional Balance Sheet Inform

Additional Balance Sheet Information	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Additional Balance Sheet Information	Additional Balance Sheet Information Certain balance sheet amounts are comprised of the following: December 31, (In thousands) 2015 2014 Accounts receivable, net Trade accounts $ 116,772 $ 227,835 Joint interest accounts 2,013 2,245 Other accounts 2,557 6,515 121,342 236,595 Allowance for doubtful accounts (1,113 ) (1,198 ) $ 120,229 $ 235,397 Inventories Tubular goods and well equipment $ 14,655 $ 10,675 Natural gas in storage 2,364 3,281 Other accounts 30 70 $ 17,049 $ 14,026 Other assets Deferred compensation plan $ 12,921 $ 13,115 Debt issuance cost 23,732 17,349 Other accounts 64 65 $ 36,717 $ 30,529 Accounts payable Trade accounts 30,038 54,949 Natural gas purchases 2,231 2,407 Royalty and other owners 75,106 97,298 Accrued capital costs 27,479 222,426 Taxes other than income 14,628 16,806 Other accounts 10,925 6,190 $ 160,407 $ 400,076 Accrued liabilities Employee benefits $ 13,870 $ 22,815 Taxes other than income 5,073 7,128 Other accounts 5,980 3,049 $ 24,923 $ 32,992 Other liabilities Deferred compensation plan $ 22,371 $ 28,932 Other accounts 3,653 10,675 $ 26,024 $ 39,607

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Year Ended December 31, (In thousands) 2015 2014 2013 Cash paid for interest and income taxes Interest $ 92,749 $ 58,487 $ 63,279 Income taxes 7,550 77,029 35,281 Non-cash investing activities Change in accrued capital costs (194,947 ) 72,603 (15,953 )

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Nature of Operations	Basis of Presentation and Nature of Operations Cabot Oil & Gas Corporation and its subsidiaries (the Company) are engaged in the development, exploitation, exploration, production and marketing of natural gas, oil and, to a lesser extent, NGLs exclusively within the continental United States. The Company also transports, stores, gathers and purchases natural gas for resale. The Company's exploration and development activities are concentrated in areas with known hydrocarbon resources, which are conducive to multi-well, repeatable drilling programs. The Company operates in one segment, natural gas and oil development, exploitation and exploration. The Company's oil and gas properties are managed as a whole rather than through discrete operating segments or business units. Operational information is tracked by geographic area; however, financial performance is assessed as a single enterprise and not on a geographic basis. Allocation of resources is made on a project basis across the Company's entire portfolio without regard to geographic areas. The consolidated financial statements include the accounts of the Company and its subsidiaries after eliminating all significant intercompany balances and transactions. Certain reclassifications have been made to prior year statements to conform with current year presentation. These reclassifications have no impact on previously reported net income (loss).
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid short-term investments with a maturity of three months or less and deposits in money market funds that are readily convertible to cash to be cash equivalents. Cash and cash equivalents were primarily concentrated in one financial institution at December 31, 2015 and 2014 . The Company periodically assesses the financial condition of its financial institutions and considers any possible credit risk to be minimal.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts The Company records an allowance for doubtful accounts for receivables that the Company determines to be uncollectible based on the specific identification method.
Inventories	Inventories Inventories are comprised of natural gas in storage, tubular goods and well equipment and pipeline imbalances. Natural gas in storage and tubular goods and well equipment balances are carried at average cost. Natural gas gathering and pipeline operations normally include imbalance arrangements with the pipeline. The volumes of natural gas due to or from the Company under imbalance arrangements are recorded at actual selling or purchase prices, as the case may be, and are adjusted monthly to market prices.
Equity Method Investments	Equity Method Investments The Company accounts for its investments in entities over which the Company has significant influence, but not control, using the equity method of accounting. Under the equity method of accounting, the Company increases its investment for contributions made and records its proportionate share of net earnings, declared dividends and partnership distributions based on the most recently available financial statements of the investee. The Company records the activity for its equity method investments on a one month lag. In addition, the Company evaluates its equity method investments for potential impairment whenever events or changes in circumstances indicate that there is an other-than-temporary decline in the value of the investment.
Properties and Equipment	Properties and Equipment The Company uses the successful efforts method of accounting for oil and gas producing activities. Under this method, acquisition costs for proved and unproved properties are capitalized when incurred. Exploration costs, including geological and geophysical costs, the costs of carrying and retaining unproved properties and exploratory dry hole drilling costs, are expensed. Development costs, including the costs to drill and equip development wells and successful exploratory drilling costs to locate proved reserves are capitalized. Exploratory drilling costs are capitalized when incurred pending the determination of whether a well has found proved reserves. The determination is based on a process which relies on interpretations of available geologic, geophysical, and engineering data. If a well is determined to be successful, the capitalized drilling costs will be reclassified as part of the cost of the well. If a well is determined to be unsuccessful, the capitalized drilling costs will be charged to exploration expense in the Consolidated Statement of Operations in the period the determination is made. If an exploratory well requires a major capital expenditure before production can begin, the cost of drilling the exploratory well will continue to be carried as an asset pending determination of whether reserves have been found only as long as: (i) the well has found a sufficient quantity of reserves to justify its completion as a producing well if the required capital expenditure is made and (ii) drilling of an additional exploratory well is under way or firmly planned for the near future. If drilling in the area is not under way or firmly planned, or if the well has not found a commercially producible quantity of reserves, the exploratory well is assumed to be impaired and its costs are charged to exploration expense. Development costs of proved oil and gas properties, including estimated dismantlement, restoration and abandonment costs and acquisition costs, are depreciated and depleted on a field basis by the units-of-production method using proved developed and proved reserves, respectively. Properties related to gathering and pipeline systems and equipment are depreciated using the straight-line method based on estimated useful lives ranging from 10 to 25 years. Generally pipeline and transmission systems are depreciated over 12 to 25 years, gathering and compression equipment is depreciated over 10 years and storage equipment and facilities are depreciated over 10 to 16 years. Buildings are depreciated on a straight-line basis over 25 to 40 years. Certain other assets are depreciated on a straight-line basis over 3 to 10 years. Costs of retired, sold or abandoned properties that make up a part of an amortization base (partial field) are charged to accumulated depreciation, depletion and amortization if the units-of-production rate is not significantly affected. A gain or loss, if any, is recognized only when a group of proved properties (entire field) that make up the amortization base has been retired, abandoned or sold. The Company evaluates its proved oil and gas properties for impairment whenever events or changes in circumstances indicate an asset's carrying amount may not be recoverable. The Company compares expected undiscounted future cash flows to the net book value of the asset. If the future undiscounted expected cash flows, based on estimates of future natural gas and crude oil prices, operating costs and anticipated production from proved reserves and risk-adjusted probable and possible reserves, are lower than the net book value of the asset, the capitalized cost is reduced to fair value. Commodity pricing is estimated by using a combination of assumptions management uses in its budgeting and forecasting process as well as historical and current prices adjusted for geographical location and quality differentials, as well as other factors that management believes will impact realizable prices. Fair value is calculated by discounting the future cash flows. The discount factor used is based on rates utilized by market participants that are commensurate with the risks inherent in the development and production of the underlying natural gas and oil. Unproved oil and gas properties are assessed periodically for impairment on an aggregate basis through periodic updates to the Company's undeveloped acreage amortization based on past drilling and exploration experience, the Company's expectation of converting leases to held by production and average property lives. Average property lives are determined on a geographical basis and based on the estimated life of unproved property leasehold rights. During 2015 , 2014 and 2013 , amortization associated with the Company's unproved properties was $41.4 million , $17.4 million and $53.6 million , respectively, and is included in depreciation, depletion, and amortization in the Consolidated Statement of Operations.
Asset Retirement Obligations	Asset Retirement Obligations The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred if a reasonable estimate of fair value can be made. The associated asset retirement cost is capitalized as part of the carrying amount of the long-lived asset. The asset retirement costs are depreciated using the units-of-production method. The majority of the asset retirement obligations recorded by the Company relate to the plugging and abandonment of oil and gas wells. However, liabilities are also recorded for meter stations, pipelines, processing plants and compressors. At December 31, 2015 , there were no assets legally restricted for purposes of settling asset retirement obligations. Additional retirement obligations increase the liability associated with new oil and gas wells and other facilities as these obligations are incurred. Accretion expense is included in depreciation, depletion and amortization expense in the Consolidated Statement of Operations.
Derivative and Hedging Activities	Derivative Instruments and Hedging Activities The Company enters into derivative contracts, primarily options and swaps, to manage its exposure to price fluctuations on a portion of its anticipated future natural gas and oil production. The Company’s credit agreement restricts the ability of the Company to enter into commodity derivatives other than to hedge or mitigate risks to which the Company has actual or projected exposure or as permitted under the Company’s risk management policies and where such derivatives do not subject the Company to material speculative risks. All of the Company’s derivatives are used for risk management purposes and are not held for trading purposes. All derivatives are recognized on the balance sheet and are measured at fair value. At the end of each quarterly period, these derivatives are marked-to-market. If the derivative does not qualify or is not designated as a cash flow hedge, changes in the fair value of the derivative are recognized in income. If the derivative qualifies and is designated as a cash flow hedge, changes in the fair value of the derivative are deferred in accumulated other comprehensive income to the extent the hedge is effective. For derivatives that qualify and are designated as a cash flow hedges, the hedging relationship between the hedging instruments and hedged items must be highly effective in achieving the offset of changes in cash flows attributable to the hedged risk, both at the inception of the hedge and on an ongoing basis. The Company measures hedge effectiveness on a quarterly basis. Hedge accounting is discontinued prospectively if and when a hedging instrument becomes ineffective. Gains and losses deferred in accumulated other comprehensive income related to cash flow hedges that become ineffective remain unchanged until the related production occurs. If the Company determines that it is probable that a forecasted hedged transaction will not occur, deferred gains or losses on the related hedging instrument are recognized in income immediately. Gains and losses on derivatives designated as cash flow hedges are included in natural gas and crude oil and condensate revenues. Gains and losses on derivatives which represent hedge ineffectiveness and gains and losses on derivatives not designated or that do not qualify for hedge accounting are included in operating revenues in gain (loss) on derivative instruments. The resulting cash flows are reported as cash flows from operating activities.
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities The Company follows the authoritative accounting guidance for measuring fair value of assets and liabilities in its financial statements. 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). The Company utilizes market data or assumptions that market participants who are independent, knowledgeable and willing and able to transact would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. The Company is able to classify fair value balances based on the observability of these inputs. The authoritative guidance for fair value measurements establishes three levels of the fair value hierarchy, defined as follows: • Level 1: Unadjusted, quoted prices for identical assets or liabilities in active markets. • Level 2: Quoted prices in markets that are not considered to be active or financial instruments for which all significant inputs are observable, either directly or indirectly for substantially the full term of the asset or liability. • Level 3: Significant, unobservable inputs for use when little or no market data exists, requiring a significant degree of judgment. The hierarchy gives the highest priority to Level 1 measurements and the lowest priority to Level 3 measurements. Depending on the particular asset or liability, input availability can vary depending on factors such as product type, longevity of a product in the market and other particular transaction conditions. In some cases, certain inputs used to measure fair value may be categorized into different levels of the fair value hierarchy. For disclosure purposes under the accounting guidance, the lowest level that contains significant inputs used in the valuation should be chosen.
Revenue Recognition	Revenue Recognition Natural gas and oil sales result from interests in oil and gas properties owned by the Company. Sales of natural gas and oil are recognized when the product is delivered and title transfers to the purchaser. Payment is generally received one to three months after the sale has occurred. Producer Gas Imbalances. The Company applies the sales method of accounting for natural gas revenue. Under this method, revenues are recognized based on the actual volume of natural gas sold to purchasers. Natural gas production operations may include joint owners who take more or less than the production volumes entitled to them on certain properties. Production volume is monitored to minimize these natural gas imbalances. Under this method, a natural gas imbalance liability is recorded if the Company's excess takes of natural gas exceed its estimated remaining proved developed reserves for these properties at the actual price realized upon the gas sale. A receivable is recognized only to the extent an imbalance cannot be recouped from the reserves in the underlying properties. The Company’s aggregate imbalance positions at December 31, 2015 and 2014 were not material. Brokered Natural Gas. Revenues and expenses related to brokering natural gas are reported gross as part of operating revenues and operating expenses in accordance with applicable accounting standards. The Company buys and sells natural gas utilizing separate purchase and sale transactions, typically with separate counterparties, whereby the Company and/or the counterparty takes title to the natural gas purchased or sold.
Income Taxes	Income Taxes The Company follows the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recorded for the estimated future tax consequences attributable to the differences between the financial carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using the tax rate in effect for the year in which those temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the year of the enacted rate change. A valuation allowance is established to reduce deferred tax assets if it is more likely than not that the related tax benefits will not be realized. The Company is required to make judgments, including estimating reserves for potential adverse outcomes regarding tax positions that the Company has taken. The Company accounts for uncertainty in income taxes using a recognition and measurement threshold for tax positions taken or expected to be taken in a tax return. The tax benefit from an uncertain tax position is recognized when it is more likely than not that the position will be sustained upon examination by taxing authorities based on technical merits of the position. The amount of the tax benefit recognized is the largest amount of the benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The effective tax rate and the tax basis of assets and liabilities reflect management's estimates of the ultimate outcome of various tax uncertainties. The Company recognizes accrued interest related to uncertain tax positions in interest expense and accrued penalties related to such positions in general and administrative expense in the Consolidated Statement of Operations.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation under the fair value method of accounting. Under this method, compensation cost is measured at the grant date for equity-classified awards and remeasured each reporting period for liability-classified awards based on the fair value of an award and is recognized over the service period, which is generally the vesting period. To calculate fair value, the Company uses either a Monte Carlo or Black-Scholes valuation model depending on the specific provisions of the award. Stock-based compensation cost for all types of awards is included in general and administrative expense in the Consolidated Statement of Operations. The tax benefit for stock-based compensation is included as both a cash outflow from operating activities and a cash inflow from financing activities in the Consolidated Statement of Cash Flows. The Company recognizes a tax benefit only to the extent it reduces the Company's income taxes payable.
Environmental Matters	Environmental Matters Environmental expenditures are expensed or capitalized, as appropriate, depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations, and that do not have future economic benefit are expensed. Liabilities related to future costs are recorded on an undiscounted basis when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated. Any insurance recoveries are recorded as assets when received.
Credit and Concentration Risk	Credit and Concentration Risk Substantially all of the Company's accounts receivable result from the sale of natural gas and oil and joint interest billings to third parties in the oil and gas industry. This concentration of purchasers and joint interest owners may impact the Company's overall credit risk, either positively or negatively, in that these entities may be similarly affected by changes in economic or other conditions. The Company does not anticipate any material impact on its financial results due to non-performance by the third parties.
Use of Estimates	Use of Estimates In preparing financial statements, the Company follows accounting principles generally accepted in the United States. These principles require management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. The most significant estimates pertain to proved natural gas and oil reserves and related cash flow estimates which are used to compute depreciation, depletion and amortization and impairments of proved oil and gas properties. Other significant estimates include natural gas and oil revenues and expenses, fair value of derivative instruments, estimates of expenses related to legal, environmental and other contingencies, asset retirement obligations, postretirement obligations, stock-based compensation and deferred income taxes. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2015-17, Balance Sheet Classification of Deferred Taxes. The amendments in this update require deferred tax liabilities and assets to be classified as noncurrent. The guidance is effective for interim and annual periods beginning after December 15, 2016, however early adoption is allowed. This update may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The Company elected to early adopt this standard on a prospective basis and, as a result, there have been no adjustments made to prior periods. The adoption of this guidance only affected the Company's financial position and did not have an impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In March 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. The amendments in this update require 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 recognition and measurement guidance for debt issuance costs are not affected by the amendments in this update. In August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements. The update provides authoritative guidance for debt issuance costs related to line-of-credit arrangements, noting the SEC staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. The guidance is effective for interim and annual periods beginning after December 15, 2015. The Company does not believe the adoption of this guidance will have a material effect on its financial position, results of operations or cash flows. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, as a new Topic, Accounting Standards Codification Topic 606. The new revenue recognition standard provides a five-step analysis of transactions to determine when and how revenue is recognized. The core principle of the guidance is that a company should recognize revenue to depict the transfer of promised 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. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606), which deferred the effective date of ASU No. 2014-09 by one year, making the new standard effective for interim and annual periods beginning after December 15, 2017. This ASU can be adopted either retrospectively or as a cumulative-effect adjustment as of the date of adoption; however, entities reporting under U.S. GAAP are not permitted to adopt the standard earlier than the original effective date for public entities (that is, no earlier than 2017 for calendar year-end entities). The Company is currently evaluating the effect that adopting this guidance will have on its financial position, results of operations or cash flows

Properties and Equipment, Net (

Properties and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Components of net property and equipment	Properties and equipment, net are comprised of the following: December 31, (In thousands) 2015 2014 Proved oil and gas properties $ 8,821,146 $ 7,984,979 Unproved oil and gas properties 390,434 492,208 Gathering and pipeline systems 243,672 241,272 Land, building and other equipment 117,848 109,758 9,573,100 8,828,217 Accumulated depreciation, depletion and amortization (4,596,221 ) (3,902,506 ) $ 4,976,879 $ 4,925,711
Schedule of net changes in capitalized exploratory well costs	The following table reflects the net changes in capitalized exploratory well costs: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of period $ 10,557 $ — $ 10,390 Additions to capitalized exploratory well costs pending the determination of proved reserves — 10,557 — Reclassifications to wells, facilities, and equipment based on the determination of proved reserves (10,557 ) — (10,198 ) Capitalized exploratory well costs charged to expense — — (192 ) Balance at end of period $ — $ 10,557 $ —
Schedule of aging of capitalized exploratory well costs	The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed: December 31, (In thousands) 2015 2014 2013 Capitalized exploratory well costs that have been capitalized for a period of one year or less $ — $ 10,557 $ — Capitalized exploratory well costs that have been capitalized for a period greater than one year — — — $ — $ 10,557 $ —

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Activity Related to Equity Method Investments	Activity related to these equity method investments is as follows: Constitution Meade Total Year Ended December 31, Year Ended December 31, Year Ended December 31, (In thousands) 2015 2014 2013 2015 2014 2013 2015 2014 2013 Balance at beginning of period $ 64,268 $ 26,892 $ 6,915 $ 3,761 $ — $ — $ 68,029 $ 26,892 $ 6,915 Contributions 19,625 34,200 18,875 9,448 3,857 — 29,073 38,057 18,875 Earnings (loss) on equity method investments 6,452 3,176 1,102 (37 ) (96 ) — 6,415 3,080 1,102 Balance at end of period $ 90,345 $ 64,268 $ 26,892 $ 13,172 $ 3,761 $ — $ 103,517 $ 68,029 $ 26,892

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of long-term debt and credit agreements	The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 75,000,000 10 years July 2011 7.26 % Tranche 2 $ 75,000,000 12 years July 2013 7.36 % Tranche 3 $ 20,000,000 15 years July 2016 7.46 % The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 88,000,000 10 years January 2021 5.42 % Tranche 2 $ 25,000,000 12 years January 2023 5.59 % Tranche 3 $ 62,000,000 15 years January 2026 5.80 % The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 245,000,000 10 years July 2018 6.44 % Tranche 2 $ 100,000,000 12 years July 2020 6.54 % Tranche 3 $ 80,000,000 15 years July 2023 6.69 % The notes have bullet maturities and were issued in three separate tranches as follows: Principal Term Maturity Date Coupon Tranche 1 $ 100,000,000 7 years September 2021 3.24 % Tranche 2 $ 575,000,000 10 years September 2024 3.67 % Tranche 3 $ 250,000,000 12 years September 2026 3.77 % The Company's debt and credit agreements consisted of the following: December 31, (In thousands) 2015 2014 Total debt 7.33% weighted-average senior notes $ 20,000 $ 20,000 6.51% weighted-average senior notes 425,000 425,000 9.78% senior notes 67,000 67,000 5.58% weighted-average senior notes 175,000 175,000 3.65% weighted-average senior notes 925,000 925,000 Revolving credit facility 413,000 140,000 Current maturities 7.33% weighted-average senior notes (20,000 ) — Long-term debt, excluding current maturities $ 2,005,000 $ 1,752,000
Schedule of credit facility	Interest rates under the amended revolving credit facility are based on LIBOR or ABR indications, plus a margin which ranges from 50 to 300 basis points, as defined in the agreement.

Derivative Instruments and He31

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Effect of Derivative Instruments on the Consolidated Balance Sheet	Effect of Derivative Instruments on the Consolidated Balance Sheet Fair Values of Derivative Instruments Derivative Assets Derivative Liabilities December 31, December 31, (In thousands) Balance Sheet Location 2015 2014 2015 2014 Derivatives Not Designated as Hedges Commodity contracts Derivative instruments (current assets) — 137,603 — — $ — $ 137,603 $ — $ —
Schedule of Offsetting of Derivative Assets and Liabilities in the Consolidated Balance Sheet	Offsetting of Derivative Assets and Liabilities in the Consolidated Balance Sheet December 31, (In thousands) 2015 2014 Derivative assets Gross amounts of recognized assets $ — $ 137,603 Gross amounts offset in the statement of financial position — — Net amounts of assets presented in the statement of financial position — 137,603 Gross amounts of financial instruments not offset in the statement of financial position — 2,338 Net amount $ — $ 139,941
Effect of Derivative Instruments on Accumulated Other Comprehensive Income (Loss)	The effective portion of gain (loss) recognized in accumulated other comprehensive income (loss) on derivatives is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Commodity contracts $ — $ (133,310 ) $ (4,523 )
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss)	The effective portion of gain (loss) reclassified from accumulated other comprehensive income (loss) into income is as follows: Year Ended December 31, (In thousands) 2015 2014 (1) 2013 Natural gas revenues $ — $ (143,577 ) $ 52,733 Crude oil and condensate revenues — (626 ) 4,269 $ — $ (144,203 ) $ 57,002 (1) The Company ceased hedge accounting effective April 1, 2014. As a result, a loss of approximately $73.4 million related to amounts previously frozen in accumulated other comprehensive income (loss) was reclassified into income during 2014.
Effect of Derivative Instruments on the Consolidated Statement of Operations	Effect of Derivative Instruments on the Consolidated Statement of Operations Year Ended December 31, (In thousands) 2015 2014 2013 Derivatives Designated as Hedges Cash received (paid) on settlement of derivative instruments Natural gas $ — $ (70,557 ) $ 52,733 Crude oil and condensate — (218 ) 4,269 $ — $ (70,775 ) $ 57,002 Derivatives Not Designated as Hedges Cash received (paid) on settlement of derivative instruments Natural gas (1) $ — $ (73,020 ) $ — Crude oil and condensate (1) — (408 ) — Gain (loss) on derivative instruments 194,289 81,716 — Non-cash gain (loss) on derivative instruments Gain (loss) on derivative instruments (137,603 ) 137,603 — $ 56,686 $ 145,891 $ — $ 56,686 $ 75,116 $ 57,002 (1) Relates entirely to the reclassification from accumulated other comprehensive income (loss) of previously frozen losses associated with derivatives that were de-designated as cash flow hedges on April 1, 2014.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Financial assets and liabilities measured at fair value on a recurring basis	The following fair value hierarchy table presents information about the Company's financial assets and liabilities measured at fair value on a recurring basis: (In thousands) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at Assets Deferred compensation plan $ 12,921 $ — $ — $ 12,921 Total assets $ 12,921 $ — $ — $ 12,921 Liabilities Deferred compensation plan $ 22,371 $ — $ — $ 22,371 Total liabilities $ 22,371 $ — $ — $ 22,371 (In thousands) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at Assets Deferred compensation plan $ 13,115 $ — $ — $ 13,115 Derivative instruments — 51,645 85,958 137,603 Total assets $ 13,115 $ 51,645 $ 85,958 $ 150,718 Liabilities Deferred compensation plan $ 28,932 $ — $ — $ 28,932 Total liabilities $ 28,932 $ — $ — $ 28,932
Fair Value of Financial Assets and Liabilities Classified as Level 3	The following table sets forth a reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of period $ 85,958 $ (3,910 ) $ 41,159 Total gains (losses) (realized or unrealized): Included in earnings 32,864 35,067 52,733 Included in other comprehensive income — 3,755 (45,069 ) Settlements (118,822 ) 51,046 (52,733 ) Transfers in and/or out of level 3 — — — Balance at end of period $ — $ 85,958 $ (3,910 ) Change in unrealized gains (losses) relating to assets and liabilities still held at the end of the period $ — $ 85,958 $ —
Carrying amounts and fair values of long-term debt	The carrying amount and fair value of debt is as follows : December 31, 2015 December 31, 2014 (In thousands) Carrying Amount Estimated Fair Value Carrying Estimated Fair Value Debt $ 2,025,000 $ 1,848,391 $ 1,752,000 $ 1,850,867 Current maturities (20,000 ) (20,378 ) — — Long-term debt, excluding current maturities $ 2,005,000 $ 1,828,013 $ 1,752,000 $ 1,850,867

Asset Retirement Obligation (Ta

Asset Retirement Obligation (Tables)	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	Activity related to the Company's asset retirement obligations is as follows: (In thousands) Year Ended Balance at beginning of period $ 126,655 Liabilities incurred 12,235 Liabilities settled (175 ) Accretion expense 6,891 Balance at end of period $ 145,606

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future minimum obligations under transportation and gathering agreements	As of December 31, 2015 , the Company's future minimum obligations under transportation and gathering agreements are as follows: (In thousands) 2016 $ 136,468 2017 178,699 2018 151,233 2019 139,387 2020 133,960 Thereafter 1,188,906 $ 1,928,653
Future minimum rental commitments under non-cancelable leases	Future minimum rental commitments under non-cancelable leases in effect at December 31, 2015 are as follows: (In thousands) 2016 $ 7,471 2017 7,036 2018 6,549 2019 6,224 2020 5,834 Thereafter 10,976 $ 44,090

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Summary of income tax expense	Income tax expense (benefit) is summarized as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Current Federal $ 983 $ 44,887 $ 56,544 State (1,397 ) (4,387 ) 10,841 (414 ) 40,500 67,385 Deferred Federal (72,869 ) (32,375 ) 111,147 State (99 ) (80,192 ) 27,233 (72,968 ) (112,567 ) 138,380 Income tax expense (benefit) $ (73,382 ) $ (72,067 ) $ 205,765
Schedule of reconciliation of actual provision for income taxes and provision for income taxes computed by applying the statutory federal income tax rate	was different than the amounts computed by applying the statutory federal income tax rate as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Statutory federal income tax rate 35 % 35 % 35 % Computed "expected" federal income tax $ (65,546 ) $ 11,341 $ 169,938 State income tax, net of federal income tax benefit (3,152 ) 903 17,513 Deferred tax adjustment related to change in overall state tax rate 2,822 (86,956 ) 15,220 Valuation allowance 187 3,977 — Uncertain tax positions — (1,974 ) 2,400 Provision to return adjustments (6,326 ) (791 ) 700 Other, net (1,367 ) 1,433 (6 ) Income tax expense (benefit) $ (73,382 ) $ (72,067 ) $ 205,765
Schedule of deferred tax liabilities and deferred tax assets	deferred tax liabilities and deferred tax assets were as follows: December 31, (In thousands) 2015 2014 Deferred Tax Assets Net operating losses $ 223,402 $ 141,961 Alternative minimum tax credits 228,693 227,719 Foreign tax credits 3,837 4,525 Incentive compensation 22,509 21,961 Deferred compensation 7,869 9,531 Post-retirement benefits 13,556 13,689 Other 2,905 5,526 Less valuation allowance (4,965 ) (4,779 ) Total 497,806 420,133 Deferred Tax Liabilities Properties and equipment 1,303,840 1,248,532 Equity method investments 1,202 — Derivative instruments — 50,750 Total 1,305,042 1,299,282 Net deferred tax liabilities $ 807,236 $ 879,149
Schedule of reconciliation of the beginning and ending amounts of unrecognized tax benefits	A reconciliation of unrecognized tax benefits is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Balance at beginning of year $ 663 $ 3,700 $ — Additions based on tax provisions related to the current year — — 3,700 Additions for tax positions of prior years — — — Reductions for tax positions of prior years — (3,037 ) — Settlements — — — Balance at end of year $ 663 $ 663 $ 3,700

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Change in the projected benefit obligation, plan assets at fair value and funded status	The change in the Company's postretirement benefit obligation is as follows: Year Ended December 31, (In thousands) 2015 2014 2013 Change in Benefit Obligation Benefit obligation at beginning of year $ 37,076 $ 34,995 $ 40,168 Service cost 1,808 1,295 1,739 Interest cost 1,448 1,343 1,500 Actuarial (gain) loss (2,829 ) 373 (7,618 ) Benefits paid (877 ) (930 ) (794 ) Benefit obligation at end of year $ 36,626 $ 37,076 $ 34,995 Change in Plan Assets Fair value of plan assets at end of year — — — Funded status at end of year $ (36,626 ) $ (37,076 ) $ (34,995 )
Schedule of amounts recognized in the balance sheet	Amounts recognized in the balance sheet consist of the following: December 31, (In thousands) 2015 2014 2013 Current liabilities $ 1,333 $ 1,249 $ 1,441 Long-term liabilities 35,293 35,827 33,554 $ 36,626 $ 37,076 $ 34,995
Schedule of amounts recognized in accumulated other comprehensive income	Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income (Loss) Year Ended December 31, (In thousands) 2015 2014 2013 Components of Net Periodic Postretirement Benefit Cost Service cost $ 1,808 $ 1,295 $ 1,739 Interest cost 1,448 1,343 1,500 Amortization of net loss — (26 ) 641 Net periodic postretirement cost $ 3,256 $ 2,612 $ 3,880 Other Changes in Benefit Obligations Recognized in Other Comprehensive Income (Loss) Net gain (loss) $ (2,829 ) $ 373 $ (7,618 ) Amortization of net (gain) loss — 26 (641 ) Total recognized in other comprehensive income (2,829 ) 399 (8,259 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 427 $ 3,011 $ (4,379 ) Amounts recognized in accumulated other comprehensive income (loss) consist of the following: December 31, (In thousands) 2015 2014 2013 Net actuarial loss $ 580 $ 3,408 $ 3,010 $ 580 $ 3,408 $ 3,010
Assumptions to determine projected postretirement benefit obligations and postretirement costs	Assumptions used to determine projected postretirement benefit obligations and postretirement costs are as follows: December 31, 2015 2014 2013 Discount rate (1) 4.25 % 4.00 % 4.75 % Health care cost trend rate for medical benefits assumed for next year 5.50 % 6.00 % 6.50 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.50 % 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate 2018 2018 2018 _______________________________________________________________________________ (1) Represents the year end rates used to determine the projected benefit obligation. To compute postretirement cost in 2015 , 2014 and 2013 , respectively, the beginning of year discount rates of 4.00% , 4.75% and 4.00% were used.
Effect of a one-percentage-point change in assumed health care cost trend rates	Assumed health care cost trend rates may have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects: (In thousands) 1-Percentage-Point Increase 1-Percentage-Point Decrease Effect on total of service and interest cost $ 618 $ (539 ) Effect on postretirement benefit obligation 5,849 (4,718 )
Schedule of estimated benefit payments	The following estimated benefit payments under the Company's postretirement plans, which reflect expected future service, are expected to be paid as follows: (In thousands) 2016 1,361 2017 1,430 2018 1,551 2019 1,718 2020 1,875 Years 2021 - 2025 11,404

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Restricted Stock Activity	The following table is a summary of restricted stock award activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 49,869 $ 33.40 27,806 $ 20.53 71,508 $ 11.82 Granted 5,900 25.44 47,500 34.76 7,200 35.70 Vested (5,944 ) 22.55 (17,437 ) 15.84 (50,902 ) 10.44 Forfeited — — (8,000 ) 35.00 — — Outstanding at end of period (1)(2) 49,825 $ 33.76 49,869 $ 33.40 27,806 $ 20.53 _______________________________________________________________________________ (1) As of December 31, 2015 , the aggregate intrinsic value was $0.9 million and was calculated by multiplying the closing market price of the Company's stock on December 31, 2015 by the number of non-vested restricted stock awards outstanding. (2) As of December 31, 2015 , the weighted average remaining contractual term of non-vested restricted stock awards outstanding was 1.2 years . The following table is a summary of restricted stock unit activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 604,214 $ 12.48 566,321 $ 10.75 515,468 $ 9.10 Granted and fully vested 51,292 27.87 37,893 38.28 50,853 27.53 Issued (230,068 ) 13.45 — — — — Forfeited — — — — — — Outstanding at end of period (1)(2) 425,438 $ 13.81 604,214 $ 12.48 566,321 $ 10.75 _______________________________________________________________________________ (1) As of December 31, 2015 , the aggregate intrinsic value was $7.5 million and was calculated by multiplying the closing market price of the Company's stock on December 31, 2015 by the number of outstanding restricted stock units. (2) Due to the immediate vesting of the units and the unknown term of each director, the weighted-average remaining contractual term in years has not been provided.
Summary of SAR activity	The following table is a summary of SAR activity: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Shares Weighted- Average Exercise Price Outstanding at beginning of period 667,764 $ 12.63 667,764 $ 12.63 1,722,444 $ 9.75 Granted — — — — — — Exercised (109,218 ) 13.19 — — (1,054,680 ) 7.92 Forfeited or expired — — — — — — Outstanding at end of period (1) 558,546 $ 12.52 667,764 $ 12.63 667,764 $ 12.63 Exercisable at end of period (2) 558,546 $ 12.52 590,960 $ 11.98 386,582 $ 11.33 _______________________________________________________________________________ (1) The intrinsic value of a SAR is the amount which the current market value of the underlying stock exceeds the exercise price of the SAR. As of December 31, 2015 , the aggregate intrinsic value and weighted-average remaining contractual term of SARs outstanding was $2.9 million and 2.2 years , respectively. (2) As of December 31, 2015 , the aggregate intrinsic value and weighted-average remaining contractual term of SARs exercisable was $2.9 million and 2.2 years , respectively.
Schedule of Performance Share Awards Activity	The following table is a summary of activity for the TSR Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share (1) Shares Weighted- Average Grant Date Fair Value per Share (1) Shares Weighted- Average Grant Date Fair Value per Share (1) Outstanding at beginning of period 674,787 $ 22.42 860,686 $ 14.06 605,706 $ 10.27 Granted 292,421 19.29 184,885 32.04 254,980 23.06 Issued and fully vested (234,922 ) 14.16 (370,784 ) 7.81 — — Forfeited — — — — — — Outstanding at end of period 732,286 $ 23.82 674,787 $ 22.42 860,686 $ 14.06 _______________________________________________________________________________ (1) The grant date fair value figures in this table represent the fair value of the equity component of the performance share awards. The following table is a summary of activity for Employee Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 1,088,960 $ 25.18 1,657,980 $ 16.25 1,919,640 $ 12.27 Granted 349,780 27.71 241,130 39.43 379,540 26.62 Issued and fully vested (504,620 ) 17.59 (751,780 ) 10.19 (610,960 ) 10.13 Forfeited (8,530 ) 31.11 (58,370 ) 23.57 (30,240 ) 17.06 Outstanding at end of period 925,590 $ 30.23 1,088,960 $ 25.18 1,657,980 $ 16.25 The following table is a summary of activity for the Hybrid Performance Share Awards: Year Ended December 31, 2015 2014 2013 Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Shares Weighted- Average Grant Date Fair Value per Share Outstanding at beginning of period 329,061 $ 29.27 450,212 $ 18.96 592,162 $ 13.11 Granted 194,947 27.71 123,257 39.43 169,980 26.62 Issued and fully vested (151,623 ) 24.56 (244,408 ) 15.41 (311,930 ) 12.03 Forfeited — — — — — — Outstanding at end of period 372,385 $ 30.37 329,061 $ 29.27 450,212 $ 18.96
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	The following assumptions were used to determine the fair value of the SEIP IV liabilities at the end of the respective periods: December 31, 2015 2014 2013 Valuation Assumptions Stock price volatility 33.9 % 33.4 % 38.0 % Risk free rate of return 1.0 % 1.0 % 1.1 % Annual salary increase rate 4.0 % 4.0 % 4.0 % Annual turnover rate 4.6 % 4.6 % 4.6 % The following assumptions were used to determine the grant date fair value of the equity component of the TSR Performance Share Awards for the respective periods: Year Ended December 31, 2015 2014 2013 Fair value per performance share award granted during the period $ 19.29 $ 32.04 $ 23.06 Assumptions Stock price volatility 32.3 % 41.3 % 43.8 % Risk free rate of return 1.0 % 0.7 % 0.4 % Expected dividend yield 0.3 % 0.2 % 0.2 % The following assumptions were used to determine the fair value of the liability component of the TSR Performance Share Awards for the respective periods: December 31, 2015 2014 2013 Fair value per performance share award at the end of the period $2.49 - $6.39 $12.88 - $29.72 $23.96 - $38.61 Assumptions Stock price volatility 33.5% - 37.5% 29.1% - 29.7% 30.2% - 35.9% Risk free rate of return 0.7% - 1.1% 0.3% - 0.7% 0.1% - 0.4% Expected dividend yield —% 0.3% 0.2%

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Calculation of basic and diluted weighted-average shares outstanding	The following is a calculation of basic and diluted weighted-average shares outstanding: December 31, (In thousands) 2015 2014 2013 Weighted-average shares - basic 413,696 415,840 420,188 Dilution effect of stock appreciation rights and stock awards at end of period — 1,761 2,187 Weighted-average shares - diluted 413,696 417,601 422,375 Weighted-average shares excluded from diluted EPS due to the anti-dilutive effect 1,481 20 5

Accumulated Other Comprehensi39

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Changes in accumulated other comprehensive income (loss) by component, net of tax	Changes in accumulated other comprehensive income (loss) by component, net of tax, were as follows: (In thousands) Net Gains (Losses) on Cash Flow Hedges Postretirement Benefits Total Balance at December 31, 2012 $ 30,717 $ (6,837 ) $ 23,880 Other comprehensive income (loss) before reclassifications (2,720 ) 4,641 1,921 Amounts reclassified from accumulated other comprehensive income (loss) (34,548 ) 386 (34,162 ) Net current-period other comprehensive income (loss) $ (37,268 ) $ 5,027 $ (32,241 ) Balance at December 31, 2013 $ (6,551 ) $ (1,810 ) $ (8,361 ) Other comprehensive income (loss) before reclassifications (80,175 ) (325 ) (80,500 ) Amounts reclassified from accumulated other comprehensive income (loss) 86,726 (16 ) 86,710 Net current-period other comprehensive income (loss) 6,551 (341 ) 6,210 Balance at December 31, 2014 $ — $ (2,151 ) $ (2,151 ) Other comprehensive income (loss) before reclassifications — 1,786 1,786 Amounts reclassified from accumulated other comprehensive income (loss) — — — Net current-period other comprehensive income (loss) — 1,786 1,786 Balance at December 31, 2015 $ — $ (365 ) $ (365 )
Schedule of amount reclassified from accumulated other comprehensive income (loss) into the Condensed Consolidated Statement of Operations	Amounts reclassified from accumulated other comprehensive income (loss) into the Consolidated Statement of Operations were as follows: Year Ended December 31, Affected Line Item in the Condensed Consolidated Statement of Operations (In thousands) 2015 2014 2013 Net gains (losses) on cash flow hedges Commodity contracts $ — $ (143,577 ) $ 52,733 Natural gas revenues Commodity contracts — (626 ) 4,269 Crude oil and condensate revenues Postretirement benefits Amortization of net (gain) loss — 26 (641 ) General and administrative expense — (144,177 ) 56,361 Total before tax — 57,467 (22,199 ) Tax expense Total reclassifications for the period $ — $ (86,710 ) $ 34,162 Net of tax

Additional Balance Sheet Info40

Additional Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Additional Balance Sheet Information	Certain balance sheet amounts are comprised of the following: December 31, (In thousands) 2015 2014 Accounts receivable, net Trade accounts $ 116,772 $ 227,835 Joint interest accounts 2,013 2,245 Other accounts 2,557 6,515 121,342 236,595 Allowance for doubtful accounts (1,113 ) (1,198 ) $ 120,229 $ 235,397 Inventories Tubular goods and well equipment $ 14,655 $ 10,675 Natural gas in storage 2,364 3,281 Other accounts 30 70 $ 17,049 $ 14,026 Other assets Deferred compensation plan $ 12,921 $ 13,115 Debt issuance cost 23,732 17,349 Other accounts 64 65 $ 36,717 $ 30,529 Accounts payable Trade accounts 30,038 54,949 Natural gas purchases 2,231 2,407 Royalty and other owners 75,106 97,298 Accrued capital costs 27,479 222,426 Taxes other than income 14,628 16,806 Other accounts 10,925 6,190 $ 160,407 $ 400,076 Accrued liabilities Employee benefits $ 13,870 $ 22,815 Taxes other than income 5,073 7,128 Other accounts 5,980 3,049 $ 24,923 $ 32,992 Other liabilities Deferred compensation plan $ 22,371 $ 28,932 Other accounts 3,653 10,675 $ 26,024 $ 39,607

Supplemental Cash Flow Inform41

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Summary of cash paid for interest and income taxes	Year Ended December 31, (In thousands) 2015 2014 2013 Cash paid for interest and income taxes Interest $ 92,749 $ 58,487 $ 63,279 Income taxes 7,550 77,029 35,281 Non-cash investing activities Change in accrued capital costs (194,947 ) 72,603 (15,953 )

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2015USD ($)CustomerInstitutionSegment	Dec. 31, 2014USD ($)CustomerInstitution	Dec. 31, 2013USD ($)Customer
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | Segment	1
Number of financial institutions | Institution	1	1
Amortization of unproved properties included in depreciation, depletion, and amortization	$ 41,400,000	$ 17,400,000	$ 53,600,000
Assets legally restricted for purposes of settling asset retirement obligations	$ 0
Sales Revenue, Net [Member] | Customer
Concentration Risk [Line Items]
Number of customers | Customer	2	2	4
Gathering and pipeline systems and equipment | Minimum
Properties and Equipment
Estimated useful life	10 years
Gathering and pipeline systems and equipment | Maximum
Properties and Equipment
Estimated useful life	25 years
Pipeline and transmission systems | Minimum
Properties and Equipment
Estimated useful life	12 years
Pipeline and transmission systems | Maximum
Properties and Equipment
Estimated useful life	25 years
Gathering and compression equipment | Maximum
Properties and Equipment
Estimated useful life	10 years
Storage equipment and facilities | Minimum
Properties and Equipment
Estimated useful life	10 years
Storage equipment and facilities | Maximum
Properties and Equipment
Estimated useful life	16 years
Buildings | Minimum
Properties and Equipment
Estimated useful life	25 years
Buildings | Maximum
Properties and Equipment
Estimated useful life	40 years
Other assets | Minimum
Properties and Equipment
Estimated useful life	3 years
Other assets | Maximum
Properties and Equipment
Estimated useful life	10 years
Customer one | Sales Revenue, Net [Member] | Customer
Concentration Risk [Line Items]
Percentage of total sales	16.00%	14.00%	21.00%
Customer two | Sales Revenue, Net [Member] | Customer
Concentration Risk [Line Items]
Percentage of total sales	14.00%	10.00%	16.00%
Customer three | Sales Revenue, Net [Member] | Customer
Concentration Risk [Line Items]
Percentage of total sales			14.00%
Customer four | Sales Revenue, Net [Member] | Customer
Concentration Risk [Line Items]
Percentage of total sales			11.00%

Acquisitions and Divestitures -

Acquisitions and Divestitures - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended					12 Months Ended
	Dec. 31, 2015	Apr. 30, 2015	Dec. 31, 2014	Oct. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Acquisitions and Disposals
Acquisitions of oil and gas						$ 16,312	$ 214,737	$ 0
Gain (loss) on sale of assets						3,866	17,120	21,351
Proceeds from sale of assets						$ 7,653	$ 39,492	323,501
Oil and gas properties, proved and unproved
Significant Acquisitions and Disposals
Gain (loss) on sale of assets								19,500
Proceeds from sale of assets								$ 44,300
Oil and gas properties, proved and unproved | Eagle Ford Shale in South Texas
Significant Acquisitions and Disposals
Acquisition cost of proved and unproved oil and gas properties			$ 30,500	$ 210,000
Acquisitions of oil and gas		$ 16,000	$ 29,900	185,200
Adjustment to acquisition cost, consents for leaseholds				17,400
Adjustment to acquisition cost, customary purchase price adjustment				7,400
Acquisition, assumed liability related to asset retirement obligations				1,200
Oil and gas properties, proved and unproved | East Texas
Significant Acquisitions and Disposals
Gain (loss) on sale of assets				19,900
Proceeds from sale of assets				$ 44,300
Oil and gas properties, proved and unproved | Oklahoma and Texas Panhandles Properties
Significant Acquisitions and Disposals
Gain (loss) on sale of assets					$ 19,400
Proceeds from sale of assets					160,000
Oil and gas properties, proved and unproved | Oklahoma Texas and Kansas Properties
Significant Acquisitions and Disposals
Gain (loss) on sale of assets					(17,500)
Proceeds from sale of assets					$ 123,400
Oil and gas properties | Significant Unobservable Inputs (Level 3)
Significant Acquisitions and Disposals
Capital rate	10.00%		10.00%

Properties and Equipment, Net -

Properties and Equipment, Net - Components of net property and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Proved oil and gas properties	$ 8,821,146	$ 7,984,979
Unproved oil and gas properties	390,434	492,208
Gathering and pipeline systems	243,672	241,272
Land, building and other equipment	117,848	109,758
Properties and equipment, gross, total	9,573,100	8,828,217
Accumulated depreciation, depletion and amortization	(4,596,221)	(3,902,506)
Properties and equipment, Net	$ 4,976,879	$ 4,925,711

Properties and Equipment, Net45

Properties and Equipment, Net - Schedule of net changes in capitalized exploratory well costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net changes in capitalized exploratory well costs
Balance at beginning of period	$ 10,557	$ 0	$ 10,390
Additions to capitalized exploratory well costs pending the determination of proved reserves	0	10,557	0
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(10,557)	0	(10,198)
Capitalized exploratory well costs charged to expense	0	0	(192)
Balance at end of period	$ 0	$ 10,557	$ 0

Properties and Equipment, Net46

Properties and Equipment, Net - Schedule of aging of capitalized exploratory well costs (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Capitalized exploratory well costs
Capitalized exploratory well costs that have been capitalized for a period of one year or less	$ 0	$ 10,557	$ 0
Capitalized exploratory well costs that have been capitalized for a period greater than one year	0	0	0
Capitalized Exploratory Well Costs	$ 0	$ 10,557	$ 0	$ 10,390

Properties and Equipment, Net47

Properties and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Properties and Equipment
Impairment of oil and gas properties	$ 114,900	$ 771,000	$ 114,875	$ 771,037	$ 0
Oil and gas properties | Significant Unobservable Inputs (Level 3)
Properties and Equipment
Capital rate	10.00%	10.00%
East And South Texas | Oil and gas properties, proved and unproved
Properties and Equipment
Sale of oil and gas properties before closing adjustments	$ 89,900	$ 86,500

Equity Method Investments - Act

Equity Method Investments - Activity Related to Equity Method Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Method Investments
Balance at beginning of period	$ 68,029	$ 26,892	$ 6,915
Contributions	29,073	38,057	18,875
Earnings (loss) on equity method investments	6,415	3,080	1,102
Balance at end of period	103,517	68,029	26,892
Constitution Pipeline Company, LLC
Equity Method Investments
Balance at beginning of period	64,268	26,892	6,915
Contributions	19,625	34,200	18,875
Earnings (loss) on equity method investments	6,452	3,176	1,102
Balance at end of period	90,345	64,268	26,892
Meade Pipeline Co LLC
Equity Method Investments
Balance at beginning of period	3,761	0	0
Contributions	9,448	3,857	0
Earnings (loss) on equity method investments	(37)	(96)	0
Balance at end of period	$ 13,172	$ 3,761	$ 0

Equity Method Investments - Nar

Equity Method Investments - Narrative (Details)	1 Months Ended		12 Months Ended
	Feb. 28, 2014mi	Apr. 30, 2012USD ($)mi	Dec. 31, 2015USD ($)investment
Schedule of Equity Method Investments [Line Items]
Equity Method Investments, Number of Investments | investment			2
Transcontinental Gas Pipe Line Company LLC
Schedule of Equity Method Investments [Line Items]
Entity's equity interest in construction agreement (as a percent)	61.00%
Constitution Pipeline Company, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)		25.00%
Length of pipeline to be constructed (in miles) | mi		124
Contribution cap		$ 250,000,000
Expected contribution in future years			$ 139,000,000
Number of year's investment expected for contribution			2 years
Meade Pipeline Co LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	20.00%
Length of pipeline to be constructed (in miles) | mi	177
Expected contribution in future years			$ 130,200,000
Number of year's investment expected for contribution			2 years
Entity's equity interest in construction agreement (as a percent)	39.00%

Debt and Credit Agreements - Sc

Debt and Credit Agreements - Schedule of debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Current maturities	$ (20,000)	$ 0
Long-term debt	2,005,000	1,752,000
7.33% weighted-average senior notes
Debt Instrument [Line Items]
Debt	20,000	20,000
Current maturities	$ (20,000)	$ 0
Weighted-average interest rate (as a percent)	7.33%	7.33%
6.51% weighted-average senior notes
Debt Instrument [Line Items]
Debt	$ 425,000	$ 425,000
Weighted-average interest rate (as a percent)	6.51%	6.51%
9.78% senior notes
Debt Instrument [Line Items]
Debt	$ 67,000	$ 67,000
Interest rate (as a percent)	9.78%	9.78%
5.58% weighted-average senior notes
Debt Instrument [Line Items]
Debt	$ 175,000	$ 175,000
Weighted-average interest rate (as a percent)	5.58%	5.58%
3.65% weighted-average senior notes
Debt Instrument [Line Items]
Debt	$ 925,000	$ 925,000
Weighted-average interest rate (as a percent)	3.65%	3.65%
Revolving credit facility
Debt Instrument [Line Items]
Debt	$ 413,000	$ 140,000

Debt and Credit Agreements - 51

Debt and Credit Agreements - Schedule of Notes Issued (Details) - Senior Notes - USD ($)	1 Months Ended
	Sep. 30, 2014	Dec. 31, 2010	Jul. 31, 2008	Jul. 31, 2001
7.33% weighted-average senior notes
Debt Instrument [Line Items]
Principal				$ 170,000,000
7.33% weighted-average senior notes | Tranche 1
Debt Instrument [Line Items]
Principal				$ 75,000,000
Term				10 years
Coupon (as a percent)				7.26%
7.33% weighted-average senior notes | Tranche 2
Debt Instrument [Line Items]
Principal				$ 75,000,000
Term				12 years
Coupon (as a percent)				7.36%
7.33% weighted-average senior notes | Tranche 3
Debt Instrument [Line Items]
Principal				$ 20,000,000
Term				15 years
Coupon (as a percent)				7.46%
6.51% weighted-average senior notes
Debt Instrument [Line Items]
Principal			$ 425,000,000
6.51% weighted-average senior notes | Tranche 1
Debt Instrument [Line Items]
Principal			$ 245,000,000
Term			10 years
Coupon (as a percent)			6.44%
6.51% weighted-average senior notes | Tranche 2
Debt Instrument [Line Items]
Principal			$ 100,000,000
Term			12 years
Coupon (as a percent)			6.54%
6.51% weighted-average senior notes | Tranche 3
Debt Instrument [Line Items]
Principal			$ 80,000,000
Term			15 years
Coupon (as a percent)			6.69%
5.58% weighted-average senior notes
Debt Instrument [Line Items]
Principal		$ 175,000,000
5.58% weighted-average senior notes | Tranche 1
Debt Instrument [Line Items]
Principal		$ 88,000,000
Term		10 years
Coupon (as a percent)		5.42%
5.58% weighted-average senior notes | Tranche 2
Debt Instrument [Line Items]
Principal		$ 25,000,000
Term		12 years
Coupon (as a percent)		5.59%
5.58% weighted-average senior notes | Tranche 3
Debt Instrument [Line Items]
Principal		$ 62,000,000
Term		15 years
Coupon (as a percent)		5.80%
3.65% weighted-average senior notes
Debt Instrument [Line Items]
Principal	$ 925,000,000
3.65% weighted-average senior notes | Tranche 1
Debt Instrument [Line Items]
Principal	$ 100,000,000
Term	7 years
Coupon (as a percent)	3.24%
3.65% weighted-average senior notes | Tranche 2
Debt Instrument [Line Items]
Principal	$ 575,000,000
Term	10 years
Coupon (as a percent)	3.67%
3.65% weighted-average senior notes | Tranche 3
Debt Instrument [Line Items]
Principal	$ 250,000,000
Term	12 years
Coupon (as a percent)	3.77%

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details)	Dec. 31, 2015USD ($)fiscal_period	Apr. 17, 2015USD ($)	Sep. 30, 2014USD ($)InvestorTranche	Dec. 31, 2010USD ($)InvestorTranche	Dec. 31, 2008USD ($)Investor	Jul. 31, 2008USD ($)InvestorTranche	Jul. 31, 2001USD ($)InvestorTranche	Dec. 31, 2015USD ($)fiscal_period	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Debt Instrument [Line Items]
2,016	$ 20,000,000							$ 20,000,000
2,018	312,000,000							312,000,000
2,020	$ 100,000,000							100,000,000
Repayments of debt								$ 604,000,000	$ 1,427,000,000	$ 895,000,000
7.33% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)	7.33%							7.33%	7.33%
Debt	$ 20,000,000							$ 20,000,000	$ 20,000,000
6.51% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)	6.51%							6.51%	6.51%
Debt	$ 425,000,000							$ 425,000,000	$ 425,000,000
9.78% senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)	9.78%							9.78%	9.78%
Debt	$ 67,000,000							$ 67,000,000	$ 67,000,000
5.58% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)	5.58%							5.58%	5.58%
Debt	$ 175,000,000							$ 175,000,000	$ 175,000,000
3.65% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)	3.65%							3.65%	3.65%
Debt	$ 925,000,000							$ 925,000,000	$ 925,000,000
Revolving credit facility
Debt Instrument [Line Items]
Minimum required asset coverage ratio								1.75
Fiscal quarters for reduction in coverage ratio | fiscal_period								4
Minimum required annual coverage ratio								2.8
Debt issuance costs	$ 7,800,000	$ 1,100,000
Maximum borrowing capacity on line of credit		3,400,000,000
Available line of credit		1,800,000,000
Minimum current ratio	1							1
Debt	$ 413,000,000							$ 413,000,000	$ 140,000,000
Remaining borrowing capacity on line of credit	$ 1,400,000,000							$ 1,400,000,000
Interest rate during period								2.20%	2.20%	2.30%
Senior Notes
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.75
Fiscal quarters for reduction in coverage ratio | fiscal_period								4
Minimum required annual coverage ratio								2.8
Deferred financing costs capitalized	$ 1,900,000							$ 1,900,000
Senior Notes | 7.33% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)	7.33%							7.33%
Principal							$ 170,000,000
Number of institutional investors | Investor							7
Number of debt tranches | Tranche							3
Principal repaid	$ 150,000,000							$ 150,000,000
Senior Notes | 6.51% weighted-average senior notes
Debt Instrument [Line Items]
Principal						$ 425,000,000
Number of institutional investors | Investor						41
Number of debt tranches | Tranche						3
Senior Notes | 9.78% senior notes
Debt Instrument [Line Items]
Principal					$ 67,000,000
Number of institutional investors | Investor					4
Term					10 years
Interest rate (as a percent)					9.78%
Senior Notes | 5.58% weighted-average senior notes
Debt Instrument [Line Items]
Principal				$ 175,000,000
Number of institutional investors | Investor				8
Number of debt tranches | Tranche				3
Senior Notes | 3.65% weighted-average senior notes
Debt Instrument [Line Items]
Weighted-average interest rate (as a percent)			3.65%
Principal			$ 925,000,000
Number of institutional investors | Investor			24
Number of debt tranches | Tranche			3
Debt issuance costs			$ 5,600,000
Revolving credit facility
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.75
Revolving credit facility | Accordion Feature, Amended Facility
Debt Instrument [Line Items]
Maximum borrowing capacity on line of credit		$ 500,000,000
Minimum | Revolving credit facility
Debt Instrument [Line Items]
Unused capacity fee percentage		0.30%
Maximum | Revolving credit facility
Debt Instrument [Line Items]
Unused capacity fee percentage		0.50%
December 31, 2016 | Senior Notes
Debt Instrument [Line Items]
Maximum leverage coverage ratio	4.75
December 31, 2016 | Revolving credit facility
Debt Instrument [Line Items]
Maximum leverage coverage ratio	4.75
December 31, 2017 | Senior Notes
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.25
Maximum leverage coverage ratio	4.25
December 31, 2017 | Revolving credit facility
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.25
Maximum leverage coverage ratio	4.25
March 31, 2018 | Senior Notes
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.75
Maximum leverage coverage ratio	3.50
March 31, 2018 | Revolving credit facility
Debt Instrument [Line Items]
Minimum required asset coverage ratio	1.75
Maximum leverage coverage ratio	3.50
Maintain coverage ratio for 2 consecutive quarters or receive investment grade rating from Standard and Poors or Moody's | Senior Notes
Debt Instrument [Line Items]
Maximum leverage coverage ratio	3
Fiscal quarters for reduction in coverage ratio | fiscal_period	2
Maintain coverage ratio for 2 consecutive quarters or receive investment grade rating from Standard and Poors or Moody's | Revolving credit facility
Debt Instrument [Line Items]
Maximum leverage coverage ratio	3							3
Fiscal quarters for reduction in coverage ratio | fiscal_period	2							2
Maintain coverage ratio for 2 consecutive quarters or receive investment grade rating from Standard and Poors or Moody's | Minimum | Revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Maintain coverage ratio for 2 consecutive quarters or receive investment grade rating from Standard and Poors or Moody's | Maximum | Revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Increase in rate based upon coverage and leverage ratio | Senior Notes
Debt Instrument [Line Items]
Basis spread on variable rate								0.00%
Increase in rate based upon coverage and leverage ratio | Minimum | Senior Notes
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Increase in rate based upon coverage and leverage ratio | Minimum | Revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Increase in rate based upon coverage and leverage ratio | Maximum | Senior Notes
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Increase in rate based upon coverage and leverage ratio | Maximum | Revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate	3.00%

Derivative Instruments and He53

Derivative Instruments and Hedging Activities - Effect of Derivatives on Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Asset	$ 0	$ 137,603
Fair Value Liability	0	0
Derivatives Not Designated as Hedges | Commodity contracts | Derivative instruments (current assets)
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Asset	0	137,603
Derivatives Not Designated as Hedges | Commodity contracts | Derivative instruments (current liabilities)
Effect of derivative instruments on the Consolidated Balance Sheet
Fair Value Liability	$ 0	$ 0

Derivative Instruments and He54

Derivative Instruments and Hedging Activities - Offsetting Assets and Liabilities in the Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative assets
Gross amounts of recognized assets	$ 0	$ 137,603
Gross amounts offset in the statement of financial position	0	0
Net amounts of assets presented in the statement of financial position	0	137,603
Gross amounts of financial instruments not offset in the statement of financial position	0	(2,338)
Net amount	$ 0	$ 139,941

Derivative Instruments and He55

Derivative Instruments and Hedging Activities - Effect of Derivative on AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commodity contracts | Derivatives designated as hedges
Derivative [Line Items]
Amount of gain (loss) recognized in OCI on derivatives (effective portion)	$ 0	$ (133,310)	$ (4,523)

Derivative Instruments and He56

Derivative Instruments and Hedging Activities - Derivative Gain(Loss) Reclassified from AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2014
Effect of derivative instruments on the Consolidated Statement of Operations
Gain (loss) related to amounts previously frozen in accumulated OCI, reclassified into income				$ (73,400)
Derivatives designated as hedges
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	$ 0	$ (144,203)	$ 57,002
Derivatives designated as hedges | Natural gas
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	0	(143,577)	52,733
Derivatives designated as hedges | Crude oil and condensate
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	$ 0	$ (626)	$ 4,269

Derivative Instruments and He57

Derivative Instruments and Hedging Activities - Effect of Derivative on Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on derivative instruments	$ 56,686	$ 219,319	$ 0
Gain (loss) in derivative instruments not designated as hedges	56,686	145,891	0
Gain (loss) on derivative, net	56,686	75,116	57,002
Derivatives designated as hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	0	(70,775)	57,002
Derivatives Not Designated as Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on derivative instruments	(137,603)	137,603	0
Natural gas | Derivatives designated as hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	0	(70,557)	52,733
Natural gas | Derivatives Not Designated as Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	0	(73,020)	0
Crude oil and condensate | Derivatives designated as hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	0	(218)	4,269
Crude oil and condensate | Derivatives Not Designated as Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	0	(408)	0
Gain (loss) on derivative instruments | Derivatives Not Designated as Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on derivative instruments	$ 194,289	$ 81,716	$ 0

Derivative Instruments and He58

Derivative Instruments and Hedging Activities - Narrative (Details) Mcf in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2016$ / McfMcf	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Apr. 01, 2014USD ($)
Derivative [Line Items]
Unrealized losses included in accumulated other comprehensive income, reclassified into natural gas and crude oil revenues , pre-tax				$ 73,400,000
Unrealized losses included in accumulated other comprehensive income, reclassified into natural gas and crude oil revenues , net of tax		$ 0		$ 44,200,000
Gain (loss) on cash flow hedge ineffectiveness		$ 0	$ 0
Subsequent Event | Energy Related Derivative | Derivatives designated as hedges | Swap
Derivative [Line Items]
Volume | Mcf	52
Swaps weighted average price (USD per Mcf) | $ / Mcf	2.51

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Deferred compensation plan	$ 12,921	$ 13,115
Derivative instruments	0	137,603
Total assets	12,921	150,718
Liabilities
Deferred compensation plan	22,371	28,932
Total liabilities	22,371	28,932
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Deferred compensation plan	12,921	13,115
Derivative instruments		0
Total assets	12,921	13,115
Liabilities
Deferred compensation plan	22,371	28,932
Total liabilities	22,371	28,932
Recurring Basis | Significant Other Observable Inputs (Level 2)
Assets
Deferred compensation plan	0	0
Derivative instruments		51,645
Total assets	0	51,645
Liabilities
Deferred compensation plan	0	0
Total liabilities	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3)
Assets
Deferred compensation plan	0	0
Derivative instruments		85,958
Total assets	0	85,958
Liabilities
Deferred compensation plan	0	0
Total liabilities	$ 0	$ 0

Fair Value Measurements - Ass60

Fair Value Measurements - Assets and Liabilities Classified as Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy
Balance at beginning of period	$ 85,958	$ (3,910)	$ 41,159
Total gains (losses) (realized or unrealized):
Included in earnings	32,864	35,067	52,733
Included in other comprehensive income	0	3,755	(45,069)
Settlements	(118,822)	51,046	(52,733)
Transfers in and/or out of level 3	0	0	0
Balance at end of period	0	85,958	(3,910)
Change in unrealized gains (losses) relating to assets and liabilities still held at the end of the period	$ 0	$ 85,958	$ 0

Fair Value Measurements - Debt

Fair Value Measurements - Debt Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair value disclosures
Current maturities	$ (20,000)	$ 0
Long-term debt	2,005,000	1,752,000
Carrying Amount
Fair value disclosures
Debt	2,025,000	1,752,000
Current maturities	(20,000)	0
Long-term debt	2,005,000	1,752,000
Estimated Fair Value
Fair value disclosures
Debt	1,848,391	1,850,867
Current maturities	(20,378)	0
Long-term debt	$ 1,828,013	$ 1,850,867

Fair Value Measurements - Narra

Fair Value Measurements - Narratives (Details)	12 Months Ended
	Dec. 31, 2015USD ($)Impaired_Asset_And_Liabilty	Dec. 31, 2014USD ($)Impaired_Asset_And_Liabilty	Dec. 31, 2013USD ($)Impaired_Asset_And_Liabilty
Fair Value Disclosures [Abstract]
Fair value assets Level 1 to Level 2 transfers amount	$ 0	$ 0	$ 0
Fair value liabilities Level 1 to Level 2 transfers amount	0	0	0
Fair value assets Level 2 to Level 1 transfers amount	0	0	0
Fair value liabilities Level 2 to Level 1 transfers amount	$ 0	$ 0	$ 0
Number of non-financial assets and liabilities impaired | Impaired_Asset_And_Liabilty	0	0	0

Asset Retirement Obligation - S

Asset Retirement Obligation - Schedule of Asset Retirement Obligation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Asset Retirement Obligation
Balance at beginning of period	$ 126,655
Liabilities incurred	12,235
Liabilities settled	(175)
Accretion expense	6,891
Balance at end of period	$ 145,606

Asset Retirement Obligation - N

Asset Retirement Obligation - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation, current	$ 2	$ 2

Commitments and Contingencies -

Commitments and Contingencies - Future Transportation and Gathering Commitments (Details) - Transportation Agreement Obligation $ in Thousands	Dec. 31, 2015USD ($)
Other Commitments [Line Items]
2,016	$ 136,468
2,017	178,699
2,018	151,233
2,019	139,387
2,020	133,960
Thereafter	1,188,906
Future transportation agreement obligation	$ 1,928,653

Commitments and Contingencies66

Commitments and Contingencies - Future Lease Commitment (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 7,471
2,017	7,036
2,018	6,549
2,019	6,224
2,020	5,834
Thereafter	10,976
Future lease payments due	$ 44,090

Commitments and Contingencies67

Commitments and Contingencies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Drilling_Rig	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Commitments and Contingencies
Rent expense	$ 13.9	$ 10.8	$ 12.3
Drilling Rig Commitments
Commitments and Contingencies
Number of drilling rig commitments | Drilling_Rig	2
2,015	$ 7.7
Minimum | Drilling Rig Commitments
Commitments and Contingencies
Drilling rig commitment term	2 years
Maximum | Drilling Rig Commitments
Commitments and Contingencies
Drilling rig commitment term	3 years

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current
Federal	$ 983	$ 44,887	$ 56,544
State	(1,397)	(4,387)	10,841
Total	(414)	40,500	67,385
Deferred
Federal	(72,869)	(32,375)	111,147
State	(99)	(80,192)	27,233
Total	(72,968)	(112,567)	138,380
Income tax (benefit) expense	$ (73,382)	$ (72,067)	$ 205,765

Income Taxes - Summary of Effec

Income Taxes - Summary of Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of actual provision for income taxes and provision for income taxes resulting from the use of federal statutory income tax
Statutory federal income tax rate (as a percent)	35.00%	35.00%	35.00%
Computed expected federal income tax	$ (65,546)	$ 11,341	$ 169,938
State income tax, net of federal income tax benefit	(3,152)	903	17,513
Deferred tax adjustment related to change in overall state tax rate	2,822	(86,956)	15,220
Valuation allowance	187	3,977	0
Uncertain tax positions	0	(1,974)	2,400
Provision to return adjustments	(6,326)	(791)	700
Other, net	(1,367)	1,433	(6)
Income tax (benefit) expense	$ (73,382)	$ (72,067)	$ 205,765

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Asset and Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets
Net operating losses	$ 223,402	$ 141,961
Alternative minimum tax credits	228,693	227,719
Foreign tax credits	3,837	4,525
Incentive compensation	22,509	21,961
Deferred compensation	7,869	9,531
Post-retirement benefits	13,556	13,689
Other	2,905	5,526
Less valuation allowance	(4,965)	(4,779)
Total	497,806	420,133
Deferred Tax Liabilities
Properties and equipment	1,303,840	1,248,532
Equity method investments	1,202	0
Derivative instruments	0	50,750
Total	1,305,042	1,299,282
Net deferred tax liabilities	$ 807,236	$ 879,149

Income Taxes - Rollforward of U

Income Taxes - Rollforward of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of unrecognized tax benefits
Balance at beginning of year	$ 663	$ 3,700	$ 0
Additions based on tax provisions related to the current year	0	0	3,700
Additions for tax positions of prior years	0	0	0
Reductions for tax positions of prior years	0	(3,037)	0
Settlements	0	0	0
Balance at end of year	$ 663	$ 663	$ 3,700

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
State tax effected net operating losses
Alternative minimum tax credits	$ 228,693	$ 227,719
Tax benefits related to employee stock-based compensation not reflected in deferred tax assets	117,800
Deferred tax adjustment related to change in overall state tax rate	2,822	(86,956)	$ 15,220
Additions based on tax provisions related to the current year	0	0	3,700
Reductions for tax positions of prior years	0	3,037	0
Unrecognized tax benefits	663	$ 663	$ 3,700	$ 0
Federal
State tax effected net operating losses
Net operating loss carryforwards	685,300
State Tax Reporting
State tax effected net operating losses
Net operating loss carryforwards	530,400
Valuation allowance on operating loss carryforwards	$ 4,600

Employee Benefit Plans - Change

Employee Benefit Plans - Change in Benefit Obligation and Fair Value (Details) - Postretirement Benefits Other than Pensions - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Benefit Obligation
Benefit obligation at beginning of year	$ 37,076	$ 34,995	$ 40,168
Service cost	1,808	1,295	1,739
Interest cost	1,448	1,343	1,500
Actuarial (gain) loss	(2,829)	373	(7,618)
Benefits paid	(877)	(930)	(794)
Benefit obligation at end of year	36,626	37,076	34,995
Change in Plan Assets
Fair value of plan assets at end of year	0	0	0
Funded status at end of year	$ (36,626)	$ (37,076)	$ (34,995)

Employee Benefit Plans - Amount

Employee Benefit Plans - Amounts Recognized in the Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amounts Recognized in the Balance Sheet
Long-term liabilities	$ 35,293	$ 35,827
Postretirement Benefits Other than Pensions
Amounts Recognized in the Balance Sheet
Current liabilities	1,333	1,249	$ 1,441
Long-term liabilities	35,293	35,827	33,554
Amounts recognized in the balance sheet	$ 36,626	$ 37,076	$ 34,995

Employee Benefit Plans - Amou75

Employee Benefit Plans - Amount Recognized in Other Comprehensive Income (Details) - Postretirement Benefits Other than Pensions - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss	$ 580	$ 3,408	$ 3,010
Amount recognized to accumulated other comprehensive income, net actuarial loss	$ 580	$ 3,408	$ 3,010

Employee Benefit Plans - Chan76

Employee Benefit Plans - Changes in Net Periodic Benefit Cost (Details) - Postretirement Benefits Other than Pensions - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of Net Periodic Postretirement Benefit Cost
Service cost	$ 1,808	$ 1,295	$ 1,739
Interest cost	1,448	1,343	1,500
Amortization of net loss	0	(26)	641
Net periodic postretirement cost	3,256	2,612	3,880
Other Changes in Benefit Obligations Recognized in Other Comprehensive Income (Loss)
Net gain (loss)	(2,829)	373	(7,618)
Amortization of net (gain) loss	0	26	(641)
Total recognized in other comprehensive income	(2,829)	399	(8,259)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 427	$ 3,011	$ (4,379)

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions in Benefit Plans (Details) - Postretirement Benefits Other than Pensions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Weighted-average assumptions used to determine projected pension benefit obligations
Discount rate (as a percent)	4.25%	4.00%	4.75%
Health care cost trend rate for medical benefits assumed for next year (as a percent)	5.50%	6.00%	6.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) (as a percent)	4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate	2,018	2,018	2,018
Discount rate beginning of year (as a percent)	4.00%	4.75%	4.00%

Employee Benefit Plans - Health

Employee Benefit Plans - Healthcare Trend Effect on Benefit Obligation (Details) - Postretirement Benefits Other than Pensions $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Effect of a one-percentage-point change in assumed health care cost trend rates
Effect of a 1 percentage-point increase in total of service and interest cost	$ 618
Effect of a 1 percentage-point decrease in total of service and interest cost	(539)
Effect of a 1 percentage-point increase in postretirement benefit obligation	(5,849)
Effect of a 1 percentage-point decrease in postretirement benefit obligation	$ (4,718)

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Estimated Future Benefit Payments (Details) - Postretirement Benefits Other than Pensions $ in Thousands	Dec. 31, 2015USD ($)
Estimated future benefit payments
2,016	$ 1,361
2,017	1,430
2,018	1,551
2,019	1,718
2,020	1,875
Years 2021 - 2025	$ 11,404

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2015USD ($)Retireeshares	Dec. 31, 2014USD ($)Retireeshares	Dec. 31, 2013USD ($)
Defined Benefit Plan Disclosure [Line Items]
Liabilities, including the Company's common stock	$ 22,371,000	$ 28,932,000
Defined contribution cost recognized	$ (6,400,000)	$ (4,900,000)	$ 7,400,000
Postretirement Benefits Other than Pensions
Defined Benefit Plan Disclosure [Line Items]
Number of retirees and dependents | Retiree	276	278
Subsidy limit percentage of expected annual fully insured premium over age threshold	60.00%
Subsidy limit percentage of expected annual fully insured premium under age threshold	$ 648,000
Annual subsidy limit percentage increases for fully insured premium over age threshold	3.50%
Estimated contributions in 2016	$ 1,400,000
Savings Investment Plan
Defined Benefit Plan Disclosure [Line Items]
Employer matching percent	6.00%
Maximum contribution, percent of employee salary	9.00%
Plan contributions charged to expense	$ 7,100,000	$ 7,200,000	6,900,000
Deferred compensation plan
Defined Benefit Plan Disclosure [Line Items]
Market value of the trust assets, excluding the Company's common stock	12,900,000	13,100,000
Liabilities, including the Company's common stock	$ 22,400,000	$ 28,900,000
Number of common stock deferred into the rabbi trust (in shares) | shares	534,174	534,174
Company's common stock held in the rabbi trust	$ 5,700,000	$ 5,700,000
Plan contributions charged to expense	(6,400,000)
Company contributions to deferred compensation plan	$ 1,000,000	$ 800,000	$ 700,000

Capital Stock - Narrative (Deta

Capital Stock - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2014
Incentive Plans
Number of shares repurchased	0	4,300,000	4,800,000
Cost of shares repurchased		$ 138,852	$ 164,634
Cumulative number of shares repurchased under a share repurchase program	29,900,000
Treasury stock, number of shares authorized to be repurchased	40,000,000
Treasury stock, cumulative shares retired	20,000,000
Cumulative cost of shares repurchased under a share repurchase program	$ 388,400
Treasury stock reissued	0
Shares held as treasury stock (in shares)	9,892,680	9,892,680
2014 Incentive Plan
Incentive Plans
Number of shares reserved for issuance				18,000,000
Number of shares available for issuance	17,100,000
2014 Incentive Plan | Stock options | Maximum
Incentive Plans
Number of shares reserved for issuance				10,000,000

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Restricted Stock Awards (Details) - Restricted Stock Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of restricted stock award activity (in shares)
Outstanding at beginning of period (in shares)	49,869	27,806	71,508
Granted (in shares)	5,900	47,500	7,200
Vested (in shares)	(5,944)	(17,437)	(50,902)
Forfeited (in shares)	0	(8,000)	0
Outstanding at end of period (in shares)	49,825	49,869	27,806
Weighted-Average Grant Date Fair Value per Share (in usd per share)
Outstanding at beginning of period (in USD per share)	$ 33.40	$ 20.53	$ 11.82
Granted (in USD per share)	25.44	34.76	35.70
Vested (in USD per share)	22.55	15.84	10.44
Forfeited (in USD per share)	0	35	0
Outstanding at end of period (in USD per share)	$ 33.76	$ 33.40	$ 20.53
Additional disclosures
Aggregate intrinsic value	$ 0.9
Weighted-average remaining contractual term of non-vested shares	1 year 2 months 9 days

Stock-Based Compensation - Sc83

Stock-Based Compensation - Schedule of Restricted Units (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of restricted stock award activity (in shares)
Outstanding at beginning of period (in shares)	604,214	566,321	515,468
Granted and fully vested (in shares)	51,292	37,893	50,853
Issued (in shares)	(230,068)	0	0
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	425,438	604,214	566,321
Weighted-Average Grant Date Fair Value per Share (in usd per share)
Outstanding at beginning of period (in USD per share)	$ 12.48	$ 10.75	$ 9.10
Granted and fully vested (USD per share)	27.87	38.28	27.53
Issued (USD per share)	13.45	0	0
Forfeited (in USD per share)	0	0	0
Outstanding at end of period (in USD per share)	$ 13.81	$ 12.48	$ 10.75
Additional disclosures
Aggregate intrinsic value	$ 7.5

Stock-Based Compensation - Sc84

Stock-Based Compensation - Schedule of Stock Appreciation Rights (Details) - Stock Appreciation Rights - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Stock Appreciation Rights Activity (in shares)
Outstanding at beginning of period (in shares)	667,764	667,764	1,722,444
Granted (in shares)		0	0
Exercised (in shares)	(109,218)	0	(1,054,680)
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	558,546	667,764	667,764
Exercisable at end of period (in shares)	558,546	590,960	386,582
Weighted-Average Exercise Price (in dollars per share)
Outstanding at beginning of period (in USD per share)	$ 12.63	$ 12.63	$ 9.75
Granted (in USD per share)		0	0
Exercised (in USD per share)	13.19	0	7.92
Forfeited (in USD per share)	0	0	0
Outstanding at end of period (in USD per share)	12.52	12.63	12.63
Exercisable at end of period (in USD per share)	$ 12.52	$ 11.98	$ 11.33
Additional disclosures
Aggregate intrinsic value	$ 2.9
Weighted-average remaining contractual term of non-vested shares	2 years 2 months 28 days
Aggregate intrinsic value of stock appreciation rights exercisable	$ 2.9
Stock appreciation rights exercisable, weighted average remaining contractual term	2 years 2 months 28 days

Stock-Based Compensation - Sc85

Stock-Based Compensation - Schedule of Performance Awards (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Performance Share Awards
Summary of employee performance share awards activity (in shares)
Outstanding at beginning of period (in shares)	1,088,960	1,657,980	1,919,640
Granted (in shares)	349,780	241,130	379,540
Issued and fully vested	(504,620)	(751,780)	(610,960)
Forfeited (in shares)	(8,530)	(58,370)	(30,240)
Outstanding at end of period (in shares)	925,590	1,088,960	1,657,980
Weighted-Average Grant Date Fair Value per Share (in usd per share)
Outstanding at beginning of period (in USD per share)	$ 25.18	$ 16.25	$ 12.27
Granted (in USD per share)	27.71	39.43	26.62
Issued and fully vested (in USD per share)	17.59	10.19	10.13
Forfeited (in USD per share)	31.11	23.57	17.06
Outstanding at end of period (in USD per share)	$ 30.23	$ 25.18	$ 16.25
Hybrid Performance Shares
Summary of employee performance share awards activity (in shares)
Outstanding at beginning of period (in shares)	329,061	450,212	592,162
Granted (in shares)	194,947	123,257	169,980
Issued and fully vested	(151,623)	(244,408)	(311,930)
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	372,385	329,061	450,212
Weighted-Average Grant Date Fair Value per Share (in usd per share)
Outstanding at beginning of period (in USD per share)	$ 29.27	$ 18.96	$ 13.11
Granted (in USD per share)	27.71	39.43	26.62
Issued and fully vested (in USD per share)	24.56	15.41	12.03
Forfeited (in USD per share)	0	0	0
Outstanding at end of period (in USD per share)	$ 30.37	$ 29.27	$ 18.96
TSR Performance Share Awards
Summary of employee performance share awards activity (in shares)
Outstanding at beginning of period (in shares)	674,787	860,686	605,706
Granted (in shares)	292,421	184,885	254,980
Issued and fully vested	(234,922)	(370,784)	0
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	732,286	674,787	860,686
Weighted-Average Grant Date Fair Value per Share (in usd per share)
Outstanding at beginning of period (in USD per share)	$ 22.42	$ 14.06	$ 10.27
Granted (in USD per share)	19.29	32.04	23.06
Issued and fully vested (in USD per share)	14.16	7.81	0
Forfeited (in USD per share)	0	0	0
Outstanding at end of period (in USD per share)	$ 23.82	$ 22.42	$ 14.06

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions for Share Based Awards (Details) - TSR Performance Share Awards - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.30%	0.20%
Stock price volatility, minimum rate	33.50%	29.10%	30.20%
Stock price volatility, maximum rate	37.50%	29.70%	35.90%
Risk free rate of return, minimum rate	0.70%	0.30%	0.10%
Risk free rate of return, maximum rate	1.10%	0.70%	0.40%
Stockholders' Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award granted during the period	$ 19.29	$ 32.04	$ 23.06
Stock price volatility	32.30%	41.30%	43.80%
Risk free rate of return	1.00%	0.70%	0.40%
Expected dividend yield	0.30%	0.20%	0.20%
Minimum | Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award granted during the period	$ 2.49	$ 12.88	$ 23.96
Maximum | Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award granted during the period	$ 6.39	$ 29.72	$ 38.61

Stock-Based Compensation - As87

Stock-Based Compensation - Assumptions for Cash Based Compensation Awards (Details) - SEIP III and SEIP IV	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Stock price volatility	33.90%	33.40%	38.00%
Risk free rate of return	1.00%	1.00%	1.10%
Annual salary increase rate	4.00%	4.00%	4.00%
Annual turnover rate	4.60%	4.60%	4.60%

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details)

Feb. 22, 2016USD ($)shares

Feb. 19, 2016performance_criteria

Jan. 05, 2016USD ($)shares

Feb. 28, 2015

Aug. 31, 2014USD ($)

Sep. 30, 2013USD ($)

Feb. 28, 2013USD ($)

Dec. 31, 2015USD ($)Award_Typeshares

Dec. 31, 2014USD ($)

Dec. 31, 2013USD ($)

Oct. 01, 2013$ / shares

Aug. 27, 2013USD ($)$ / shares

Feb. 11, 2013USD ($)$ / shares

May. 01, 2012$ / shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

$ 13,700,000

$ 21,500,000

$ 51,800,000

Stock-based compensation tax benefit

0

(1,375,000)

18,913,000

Defined contribution cost recognized

$ (6,400,000)

(4,900,000)

7,400,000

Deferred Compensation, Share-based Payments

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common shares held in employee trust earned but not distributed (in shares) | shares

534,174

Shares issued in period (in shares) | shares

0

Restricted Stock Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

$ 400,000

1,000,000

200,000

Award vesting period

3 years

Compensation cost not yet recognized

$ 500,000

Fair value of award

200,000

600,000

1,600,000

Aggregate intrinsic value

$ 900,000

Weighted-average remaining contractual term of non-vested shares

1 year 2 months 9 days

Restricted Stock Awards | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected forfeiture rate

5.00%

Restricted Stock Awards | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected forfeiture rate

6.00%

Restricted Stock Awards | Graduated or graded vesting | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting period

3 years

Restricted Stock Awards | Graduated or graded vesting | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting period

4 years

Restricted Stock Units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

$ 1,400,000

1,500,000

1,400,000

Aggregate intrinsic value

$ 7,500,000

Stock Appreciation Rights

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

100,000

300,000

Compensation cost not yet recognized

0

Term of award

7 years

Aggregate intrinsic value

$ 2,900,000

Weighted-average remaining contractual term of non-vested shares

2 years 2 months 28 days

Stock Appreciation Rights | Graduated or graded vesting

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting period

3 years

Award vesting percentage

33.33%

Performance Shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

$ 18,300,000

20,800,000

30,900,000

Award vesting period

3 years

Compensation cost not yet recognized

$ 18,400,000

Number of performance award types | Award_Type

3

Period of recognition for unrecognized compensation costs

1 year 15 days

Aggregate intrinsic value

$ 35,900,000

Weighted-average remaining contractual term of non-vested shares

1 year 1 month 10 days

Number of performance awards where the performance period has ended | Award_Type

2

Performance Shares | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected forfeiture rate

0.00%

Performance Shares | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected forfeiture rate

6.00%

Internal Metrics Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of performance award types | Award_Type

2

Rights to share portion of award, maximum percent

100.00%

Market Based Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of performance award types | Award_Type

1

Rights to share portion of award, maximum percent

100.00%

Rights to cash portion of award, maximum percent

100.00%

Employee Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting period

3 years

3 years

Employee Performance Share Awards | Performance metric: average production

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting percentage

33.33%

Employee Performance Share Awards | Performance metric: average finding costs

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting percentage

33.33%

Employee Performance Share Awards | Performance metric: average reserve replacement

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting percentage

33.33%

Hybrid Performance Shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Minimum operating cash flow for performance based award

$ 100,000,000

Hybrid Performance Shares | Graduated or graded vesting

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting period

3 years

Hybrid Performance Shares | 25% vesting on first and second anniversary

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting percentage

25.00%

Hybrid Performance Shares | 50% vesting on third anniversary

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Award vesting percentage

50.00%

TSR Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance period of peer group

3 years

Cash payments for share-based compensation

$ 7,000,000

14,300,000

0

TSR Performance Share Awards | Liability

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Current portion of share-based liability

1,800,000

7,000,000

Noncurrent portion of share-based liability

900,000

4,000,000

SEIP

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share-based compensation expense

$ (300,000)

3,000,000

$ 11,500,000

Number of trading days during which the closing price meets or exceeds the goal price

20 days

Number of consecutive trading days for payout

60 days

Period for interim goal

2 years

Period for final goal

4 years

Percent of employee salary for interim goal

20.00%

Percent of employee salary for final goal

50.00%

Percent of employee salary if interim goal is met

30.00%

Percentage of aggregate distribution to be paid immediately

25.00%

Percentage of aggregate distribution to be paid on deferred dates

75.00%

Payments Related to Share Based Compensation

$ 13,000,000

SEIP | Percent paid in last 18 months

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of aggregate distribution to be paid immediately

100.00%

SEIP III

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Interim goal price (in USD per share) | $ / shares

$ 25

$ 25

Final goal price (in USD per share) | $ / shares

$ 37.50

$ 37.50

Interim goal payable

$ 6,800,000

Percent of interim goal paid

75.00%

25.00%

Interim goal payment

$ 4,900,000

$ 1,700,000

Final goal payable

$ 11,100,000

Percent of final goal paid

75.00%

25.00%

Final goal payment

$ 8,100,000

$ 2,800,000

SEIP IV

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Interim goal price (in USD per share) | $ / shares

$ 55

Final goal price (in USD per share) | $ / shares

$ 80

Final goal payable

$ 0

Subsequent Event | Employee Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of performance criteria | performance_criteria

3

Number of performance awards issued and certified (in shares) | shares

340,960

Grant date fair value of performance shares issued and certified

$ 9,100,000

Subsequent Event | TSR Performance Share Awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of performance awards issued and certified (in shares) | shares

254,980

Grant date fair value of performance shares issued and certified

$ 5,900,000

Cash component of performance share award

$ 1,800,000

Earnings per Common Share - Sch

Earnings per Common Share - Schedule of EPS (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Weighted-average shares - basic (in shares)	413,696	415,840	420,188
Dilution effect of stock options, stock appreciation rights and stock awards at end of period (in shares)	0	1,761	2,187
Weighted-average shares - diluted (in shares)	413,696	417,601	422,375
Weighted-average shares excluded from diluted EPS due to the anti-dilutive effect (in shares)	1,481	20	5

Accumulated Other Comprehensi90

Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in accumulated other comprehensive income (loss) by component, net of tax
Balance at beginning of period	$ 2,142,733	$ 2,204,602	$ 2,131,447
Other comprehensive income (loss) before reclassifications	1,786	(80,500)	1,921
Amounts reclassified from accumulated other comprehensive income (loss)	0	86,710	(34,162)
Total other comprehensive income (loss)	1,786	6,210	(32,241)
Balance at end of period	2,009,188	2,142,733	2,204,602
Net Gains (Losses) on Cash Flow Hedges
Changes in accumulated other comprehensive income (loss) by component, net of tax
Balance at beginning of period	0	(6,551)	30,717
Other comprehensive income (loss) before reclassifications	0	(80,175)	(2,720)
Amounts reclassified from accumulated other comprehensive income (loss)	0	86,726	(34,548)
Total other comprehensive income (loss)	0	6,551	(37,268)
Balance at end of period	0	0	(6,551)
Postretirement Benefits
Changes in accumulated other comprehensive income (loss) by component, net of tax
Balance at beginning of period	(2,151)	(1,810)	(6,837)
Other comprehensive income (loss) before reclassifications	1,786	(325)	4,641
Amounts reclassified from accumulated other comprehensive income (loss)	0	(16)	386
Total other comprehensive income (loss)	1,786	(341)	5,027
Balance at end of period	(365)	(2,151)	(1,810)
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component, net of tax
Balance at beginning of period	(2,151)	(8,361)	23,880
Balance at end of period	$ (365)	$ (2,151)	$ (8,361)

Accumulated Other Comprehensi91

Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line items in income statement impacted by reclassifications out of accumulated other comprehensive income
Natural gas revenues	$ 1,025,044	$ 1,590,625	$ 1,405,262
Crude oil and condensate revenues	248,211	313,889	291,418
Income (loss) before income taxes	(187,273)	32,401	485,538
Tax expense	73,382	72,067	(205,765)
Net income (loss)	(113,891)	104,468	279,773
Amount Reclassified from Accumulated Other Comprehensive Income
Line items in income statement impacted by reclassifications out of accumulated other comprehensive income
Income (loss) before income taxes	0	(144,177)	56,361
Tax expense	0	57,467	(22,199)
Net income (loss)	0	(86,710)	34,162
Net gains (losses) on cash flow hedges | Amount Reclassified from Accumulated Other Comprehensive Income | Commodity contracts
Line items in income statement impacted by reclassifications out of accumulated other comprehensive income
Natural gas revenues	0	(143,577)	52,733
Crude oil and condensate revenues	0	(626)	4,269
Amortization of net (gain) loss | Amount Reclassified from Accumulated Other Comprehensive Income
Line items in income statement impacted by reclassifications out of accumulated other comprehensive income
Amortization of net (gain) loss	$ 0	$ 26	$ (641)

Additional Balance Sheet Info92

Additional Balance Sheet Information - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, net
Trade accounts	$ 116,772	$ 227,835
Joint interest accounts	2,013	2,245
Income taxes receivable	4,323	3,612
Other accounts	2,557	6,515
Receivables gross current	121,342	236,595
Allowance for doubtful accounts	(1,113)	(1,198)
Accounts receivable, net	120,229	235,397
Inventories
Tubular goods and well equipment	2,364	3,281
Natural gas in storage	14,655	10,675
Other accounts	30	70
Inventory, net	17,049	14,026
Other assets
Deferred compensation plan	12,921	13,115
Debt issuance cost	23,732	17,349
Other accounts	64	65
Other assets	36,717	30,529
Accounts payable
Trade accounts	30,038	54,949
Natural gas purchases	2,231	2,407
Royalty and other owners	75,106	97,298
Accrued capital costs	27,479	222,426
Taxes other than income	14,628	16,806
Other accounts	10,925	6,190
Accounts payable current	160,407	400,076
Accrued liabilities
Employee benefits	13,870	22,815
Taxes other than income	5,073	7,128
Interest payable	30,222	30,677
Other accounts	5,980	3,049
Accrued liabilities	24,923	32,992
Other liabilities
Deferred compensation plan	22,371	28,932
Other accounts	3,653	10,675
Other liabilities	$ 26,024	$ 39,607

Supplemental Cash Flow Inform93

Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash paid for interest and income taxes
Interest	$ 92,749	$ 58,487	$ 63,279
Income taxes	7,550	77,029	35,281
Change in accrued capital costs	$ (194,947)	$ 72,603	$ (15,953)