CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income	$ 106,030	$ 144,246
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on divestiture activity	(54,934)	(127,999)
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	220,738	157,535
Exploratory dry hole expense	49	327
Abandonment and impairment of unproved properties	4,316	3,279
Stock-based compensation expense	11,837	11,864
Change in Net Profits Plan liability	211	(33,871)
Unrealized derivative (gain) loss	24,160	(9,822)
Amortization of debt discount and deferred financing costs	11,294	6,657
Deferred income taxes	52,241	78,820
Plugging and abandonment	(1,430)	(6,222)
Other	(5,888)	2,937
Changes in current assets and liabilities:
Accounts receivable	(10,370)	7,628
Refundable income taxes	5,348	9,558
Prepaid expenses and other	15,692	(148)
Accounts payable and accrued expenses	(2,530)	26,299
Excess income tax benefit from the exercise of stock awards	(6,791)	(938)
Net cash provided by operating activities	369,973	270,150
Cash flows from investing activities:
Net proceeds from sale of oil and gas properties	97,952	247,998
Capital expenditures	(662,372)	(304,627)
Deposits to restricted cash		(19,595)
Other	(2,355)	(6,492)
Net cash used in investing activities	(566,775)	(82,716)
Cash flows from financing activities:
Proceeds from credit facility	102,000	204,059
Repayment of credit facility	(150,000)	(392,059)
Debt issuance costs related to credit facility	(8,525)
Net proceeds from 6.625% Senior Notes	341,435
Proceeds from sale of common stock	4,929	2,916
Dividends paid	(3,181)	(3,144)
Excess income tax benefit from the exercise of stock awards	6,791	938
Other	(644)	(544)
Net cash provided by (used in) financing activities	292,805	(187,834)
Net change in cash and cash equivalents	96,003	(400)
Cash and cash equivalents at beginning of period	5,077	10,649
Cash and cash equivalents at end of period	101,080	10,249
Supplemental schedule of additional cash flow information and noncash investing and financing activities:
Cash paid for interest	(6,378)	(8,152)
Net cash refunded for income taxes	$ 2,543	$ 2,392