Consolidated Statement of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income (loss)	$ (40,248,000)	$ 506,877,000	$ 227,959,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	485,322,000	412,334,000	307,055,000
Gain on sale of properties	0	(186,999,000)	0
Impairment of oil and gas properties	46,109,000	47,238,000	1,168,000
Deferred income taxes	(16,114,000)	307,457,000	134,583,000
Derivative instruments	(210,376,000)	(327,011,000)	35,432,000
Stock-based compensation expenses	25,272,000	21,302,000	11,982,000
Deferred financing costs amortization and other	12,299,000	11,028,000	4,248,000
Working capital and other changes:
Change in accounts receivable	108,461,000	16,702,000	(107,473,000)
Change in inventory	6,873,000	(3,776,000)	(13,941,000)
Change in prepaid expenses	1,828,000	(3,199,000)	(8,191,000)
Change in other current assets	6,489,000	(6,135,000)	(56,000)
Change in other assets	(950,000)	114,000	(3,248,000)
Change in accounts payable and accrued liabilities	(71,617,000)	76,723,000	107,451,000
Change in other current liabilities	6,500,000	0	0
Change in other liabilities	(33,000)	(139,000)	887,000
Net cash provided by operating activities	359,815,000	872,516,000	697,856,000
Cash flows from investing activities:
Capital expenditures	(819,847,000)	(1,354,281,000)	(893,524,000)
Acquisition of oil and gas properties	(28,817,000)	(46,247,000)	(1,560,072,000)
Proceeds from sale of properties	1,075,000	324,852,000	0
Costs related to sale of properties	0	(2,337,000)	0
Derivative settlements	370,410,000	6,774,000	(8,133,000)
Redemptions of short-term investments	0	0	25,000,000
Advances from joint interest partners	(1,969,000)	(6,213,000)	(8,347,000)
Net cash used in investing activities	(479,148,000)	(1,077,452,000)	(2,445,076,000)
Cash flows from financing activities:
Proceeds from issuance of senior notes	0	0	1,000,000,000
Proceeds from revolving credit facility	630,000,000	620,000,000	600,000,000
Principal payments on revolving credit facility	(992,000,000)	(455,570,000)	(264,430,000)
Deferred financing costs	(14,632,000)	(99,000)	(22,910,000)
Proceeds from sale of common stock	462,833,000	0	314,580,000
Purchases of treasury stock	(2,949,000)	(5,309,000)	(1,566,000)
Other	0	(176,000)	0
Net cash provided by financing activities	83,252,000	158,846,000	1,625,674,000
Decrease in cash and cash equivalents	(36,081,000)	(46,090,000)	(121,546,000)
Cash and cash equivalents:
Beginning of period	45,811,000	91,901,000	213,447,000
End of period	9,730,000	45,811,000	91,901,000
Supplemental cash flow information:
Cash paid for interest, net of capitalized interest	145,333,000	150,181,000	85,596,000
Cash paid for taxes	0	5,329,000	750,000
Cash received for income tax refunds	5,548,000	0	0
Supplemental non-cash transactions:
Change in accrued capital expenditures	(260,060,000)	169,710,000	34,354,000
Change in asset retirement obligations	$ 3,972,000	$ 6,182,000	$ 13,201,000