Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:
Net Income (Loss) Attributable to Parent	$ 237,838,000	$ (2,176,898,000)	$ 453,202,000
Adjustments to reconcile net (Loss) income to cash provided by operating activities:
Depletion and depreciation	243,390,000	388,985,000	346,394,000
Ceiling test and other impairments	0	2,972,464,000	0
Deferred gain on sale of liquids gathering system	(10,553,000)	0	0
Deferred and current non-cash income taxes	(6,000)	(712,576,000)	251,206,000
Unrealized loss (gain) on commodity derivatives	25,876,000	230,385,000	(100,383,000)
Excess tax benefit from stock based compensation	0	4,427,000	(6,212,000)
Stock compensation	9,767,000	10,756,000	13,919,000
Other	2,252,000	3,667,000	1,495,000
Net changes in operating assets and liabilities:
Restricted cash	2,000	0	(23,000)
Accounts receivable	16,565,000	62,758,000	(26,910,000)
Prepaid expenses and other	1,180,000	1,740,000	(4,993,000)
Other non-current assets	277,000	284,000	0
Accounts payable	(1,400,000)	(37,964,000)	(15,567,000)
Accrued liabilities	(32,904,000)	(77,633,000)	101,646,000
Production taxes payable	(7,207,000)	(14,372,000)	8,735,000
Interest payable	1,772,000	(213,000)	3,428,000
Other long-term obligations	3,296,000	(9,031,000)	433,000
Current taxes payable	(17,507,000)	8,046,000	6,922,000
Net cash provided by operating activities	472,638,000	654,825,000	1,033,292,000
Investing Activities:
Acquisition costs	(649,801,000)	0	0
Oil and gas property expenditures	(370,662,000)	(708,017,000)	(1,435,611,000)
Gathering system expenditures	(5,510,000)	(127,149,000)	(83,996,000)
Proceeds from sale of oil and gas properties	0	0	5,821,000
Proceeds from sale of liquids gathering system	(129,000)	203,046,000	0
Proceeds from sale of marketable securities	0	21,235,000	0
Change in capital cost accrual	(65,975,000)	38,338,000	125,261,000
Inventory	(627,000)	(374,000)	1,595,000
Purchase of property, plant and equipment	(815,000)	(4,302,000)	(21,865,000)
Net cash used in investing activities	(1,093,519,000)	(577,223,000)	(1,408,795,000)
Financing activities:
Borrowings on long-term debt	1,006,000,000	852,000,000	1,257,000,000
Payments on long-term debt	(823,000,000)	(918,000,000)	(914,000,000)
Proceeds from issuance of Senior Notes	450,000,000	0	0
Deferred financing costs	(8,958,000)	0	(6,866,000)
Repurchased shares/net share settlements	(5,429,000)	(6,718,000)	(36,298,000)
Excess tax benefit from stock based compensation	0	(4,427,000)	6,212,000
Proceeds from exercise of options	11,000	1,157,000	9,928,000
Net cash provided by (used in) financing activities	618,624,000	(75,988,000)	315,976,000
(Decrease)/increase in cash during the period	(2,257,000)	1,614,000	(59,527,000)
Cash and cash equivalents, beginning of period	12,921,000	11,307,000	70,834,000
Cash and cash equivalents, end of period	10,664,000	12,921,000	11,307,000
Cash paid for:
Interest	99,542,000	101,237,000	88,964,000
Income taxes	13,843,000	4,379,000	7,260,000
Non Cash Investing Activities Oil And Gas Properties	$ 12,651,000	$ 0	$ 0