Consolidated Statements of Cash Flows (Audited) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income (loss)	$ (68,280,000)	$ 155,435,000	$ (22,301,000)
Adjustments to net income (loss) to reconcile to net cash provided by operating activities:
Net change in fair value of unsettled derivatives	35,791,000	(311,281,000)	36,801,000
Depreciation, depletion and amortization	303,258,000	201,656,000	129,518,000
Impairment of natural gas and crude oil properties	161,620,000	167,280,000	53,802,000
Accretion of asset retirement obligation	6,293,000	3,455,000	4,747,000
Stock-based compensation	20,068,000	17,518,000	12,880,000
Excess tax benefits from stock-based compensation	(1,361,000)	(1,999,000)	(2,489,000)
(Gain) loss from sale of properties and equipment	385,000	75,972,000	(3,722,000)
Amortization of debt discount and issuance costs	7,040,000	6,938,000	6,783,000
Deferred income taxes	(41,415,000)	88,474,000	(15,883,000)
Inventory adjustment and other	(1,855,000)	(1,329,000)	170,000
Total adjustments to net income (loss) to reconcile to net cash provided by operating activities:	489,054,000	94,740,000	230,051,000
Changes in current assets and liabilities:
Accounts receivable	24,769,000	(34,598,000)	(41,509,000)
Other assets	(2,264,000)	(3,296,000)	3,461,000
Restricted cash	46,000	2,214,000	(8,000)
Production tax liability	(1,629,000)	3,358,000	4,121,000
Accounts payable and accrued expenses	(30,310,000)	21,453,000	(11,485,000)
Other liabilities	(313,000)	(2,617,000)	(3,165,000)
Total changes in current assets and liabilities	(9,701,000)	(13,486,000)	(48,585,000)
Net cash provided by operating activities	411,073,000	236,689,000	159,165,000
Cash flows from investing activities:
Capital expenditures	(604,668,000)	(628,592,000)	(394,948,000)
Acquisition of natural gas and crude oil properties, net of cash acquired	0	0	(9,658,000)
Proceeds from acquisition adjustments	0	0	7,579,000
Proceeds from sale of properties and equipment	405,000	154,457,000	179,919,000
Net cash used in investing activities	(604,263,000)	(474,135,000)	(217,108,000)
Cash flows from financing activities:
Proceeds from credit facility	397,000,000	263,750,000	260,250,000
Payment of credit facility	416,000,000	200,000,000	283,500,000
Payment of debt issuance costs	(974,000)	(88,000)	(2,352,000)
Proceeds from sale of equity, net of issuance costs	202,851,000	0	275,847,000
Excess tax benefits from stock-based compensation	1,361,000	1,999,000	2,489,000
Purchase of treasury stock	(6,056,000)	(5,392,000)	(4,133,000)
Principal payments under capital lease obligations	(208,000)	0	0
Proceeds from exercise of stock options	0	0	128,000
Net cash provided by (used in) financing activities	177,974,000	60,269,000	248,729,000
Net increase (decrease) in cash and cash equivalents	(15,216,000)	(177,177,000)	190,786,000
Cash and cash equivalents, beginning of year	16,066,000	193,243,000	2,457,000
Cash and cash equivalents, end of year	850,000	16,066,000	193,243,000
Cash payments (receipts) for:
Interest, net of capitalized interest	45,642,000	46,809,000	48,844,000
Income taxes	10,049,000	1,800,000	(3,014,000)
Non-cash investing activities:
Change in accounts payable related to purchases of properties and equipment	(45,230,000)	39,667,000	33,328,000
Change in asset retirement obligation, with a corresponding increase to natural gas and crude oil properties, net of disposals	14,030,000	33,250,000	2,112,000
Change in accounts receivable related to disposition of properties and equipment	0	0	808,000
Change in other assets related to disposition of properties and equipment	0	39,048,000	3,350,000
Purchase of properties and equipment under capital leases	$ 1,601,000	$ 0	$ 0