Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of the provision for income taxes
Federal	$ 2,932	$ 0	$ 0
State	1,539	1,571	868
Deferred portion of income tax expense (benefit)	(448,643)	(276,722)	397,780
Income tax expense (benefit)	$ (444,172)	$ (275,151)	$ 398,648
Effective tax rate (as a percent)	37.00%	38.10%	37.40%
Deferred Income Taxes [Abstract]
Deferred Tax Liabilities, Oil and Gas Properties	$ 518,394	$ 854,029
Deferred Tax Liabilities, Derivative asset	0	179,543
Deferred Tax Liabilities, Other	7,733	1,233
Deferred Tax Liabilities	526,127	1,034,805
Deferred Tax Assets, Federal and State Tax Net Operating Loss Carryforwards	151,343	244,942
Deferred Tax Assets, Derivative Instruments	31,349	0
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	10,083	14,529
Deferred Tax Assets, Tax Credit Carryforwards	12,448	6,952
Deferred Tax Assets, Other Liabilities	10,567	20,497
Deferred Tax Assets, Gross	215,790	286,920
Deferred Tax Assets, Valuation Allowance	(5,335)	(10,394)
Deferred Tax Assets, Net	210,455	276,526
Deferred Tax Liabilities, Net	315,672	758,279
Unrecognized Tax Benefits, Exercise of Stock Awards	126,700
Tax Credit Recorded for IRS R&D Settlement		2,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning Balance	2,782	1,582	$ 2,358
Unrecognized Tax Benefits, Additions For Tax Positions Of Prior Years	9	1,200	140
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(2,345)	0	(916)
Unrecognized Tax Benefits, Ending Balance	446	2,782	$ 1,582
State and Local Jurisdiction [Member]
Deferred Income Taxes [Abstract]
Income Taxes Receivable, Current	0	65
Taxes Payable, Current	1,181	0
Operating Loss Carryforwards	184,600
General Business Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Deferred Income Taxes [Abstract]
Tax Credit Carryforward, Amount	528
Internal Revenue Service (IRS) [Member] | Domestic Tax Authority [Member]
Deferred Income Taxes [Abstract]
Income Taxes Receivable, Current	644	$ 5,378
Operating Loss Carryforwards	540,200
Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member] | Domestic Tax Authority [Member]
Deferred Income Taxes [Abstract]
Tax Credit Carryforward, Amount	7,200
Internal Revenue Service (IRS) [Member] | Alternative Minimum Tax Credit Carryforward [Member] | Domestic Tax Authority [Member]
Deferred Income Taxes [Abstract]
Tax Credit Carryforward, Amount	$ 5,600