CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 51,225,000	$ 106,030,000
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on divestiture activity	22,714,000	(54,934,000)
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	331,178,000	220,738,000
Exploratory dry hole expense	8,198,000	49,000
Impairment of proved properties	38,523,000	0
Abandonment and impairment of unproved properties	10,849,000	4,316,000
Share-based Compensation	12,372,000	11,837,000
Change in Net Profits Plan liability	(18,140,000)	211,000
Unrealized derivative gain	(74,014,000)	24,160,000
Amortization of debt discount and deferred financing costs	4,616,000	11,294,000
Deferred income taxes	30,215,000	52,241,000
Plugging and abandonment	(1,516,000)	(1,430,000)
Other	(867,000)	(5,888,000)
Changes in current assets and liabilities:
Accounts receivable	735,000	(10,370,000)
Refundable income taxes	2,978,000	5,348,000
Prepaid expenses and other	(4,759,000)	15,692,000
Accounts payable and accrued expenses	(4,019,000)	(2,530,000)
Excess income tax benefit from the exercise of stock awards	0	(6,791,000)
Net cash provided by operating activities	410,288,000	369,973,000
Cash flows from investing activities:
Net proceeds from sale of oil and gas properties	15,410,000	97,952,000
Capital expenditures	(705,366,000)	(662,372,000)
Payments to Acquire Oil and Gas Property	(5,312,000)	0
Other	111,000	(2,355,000)
Net cash used in investing activities	(695,157,000)	(566,775,000)
Cash flows from financing activities:
Proceeds from credit facility	802,500,000	102,000,000
Repayment of credit facility	(741,500,000)	(150,000,000)
Debt issuance costs related to credit facility	0	(8,525,000)
Proceeds from Issuance of 6.50% Senior Notes due 202	392,336,000	0
Proceeds from Issuance of 6.625% Senior Notes	0	341,435,000
Repayments of Convertible Debt	(287,500,000)	0
Proceeds from sale of common stock	2,888,000	4,929,000
Dividends paid	(3,208,000)	(3,181,000)
Excess income tax benefit from the exercise of stock awards	0	6,791,000
Other	343,000	(644,000)
Net cash provided by (used in) financing activities	165,859,000	292,805,000
Net change in cash and cash equivalents	(119,010,000)	96,003,000
Cash and cash equivalents at beginning of period	119,194,000	5,077,000
Cash and cash equivalents at end of period	184,000	101,080,000
Supplemental schedule of additional cash flow information and noncash investing and financing activities:
Cash paid for interest	(30,137,000)	(6,378,000)
Net cash refunded for income taxes	2,815,000	2,543,000
Capital Expenditures Incurred but Not yet Paid	$ 226,000,000	$ 237,900,000