Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net earnings	$ 133,040	$ 186,670
Depreciation, depletion and amortization	160,251	160,136
Gain on sale of assets	(1,770)	0
Gain on purchase	0	(1,046)
Extinguishment of debt	6,842	3,377
Amortization of debt issuance costs and net discount	5,350	6,261
Impairment of oil and natural gas properties	67	0
Dry Hole and Impairment	2,515	316
Derivatives	(34,760)	(139,683)
Stock-based compensation expense	7,589	7,451
Deferred income taxes	77,511	105,096
Other, net	(1,620)	(275)
Allowance for bad debt	450	0
Change in book overdraft	7,573	5,359
Changes in operating assets and liabilities:
Accounts receivable	504	(24,614)
Inventories, prepaid expenses, and other current assets	(2,634)	(2,263)
Accounts payable and revenue and royalties payable	15,097	48,438
Accrued interest and other accrued liabilities	15,611	16,667
Net cash provided by (used in) operating activities	391,616	371,890
Cash flows from investing activities:
Exploration and development of oil and natural gas properties	(524,036)	(424,144)
Property acquisitions	(75,706)	(155,443)
Capitalized interest	(13,977)	(24,236)
Proceeds from sale of assets	17,294	0
Deposits on asset sales	(3,300)	0
Net cash used in investing activities	(599,725)	(603,823)
Cash flows from financing activities:
Proceeds from issuances on line of credit	0	368,100
Payments on borrowings under line of credit	0	(355,900)
Proceeds from issuance of 6.375% Senior notes due 2022	600,000	0
Repurchase of 8.25% Senior subordinated notes due 2016	(200,000)	0
Repurchase of 10.25% Senior notes due 2014	(149,999)	(91,044)
Long-term borrowings under credit facility	1,215,500	529,400
Repayments of long-term borrowings under credit facility	(1,237,000)	(214,400)
Financing obligation	(309)	(281)
Debt issuance costs	(11,424)	(1,176)
Dividends paid	(13,160)	(12,480)
Stock options and restricted stock issued	3,551	7,333
Excess income tax benefit	756	2,197
Net cash provided by financing activities	207,915	231,749
Net decrease in cash and cash equivalents	(194)	(184)
Cash and cash equivalents at beginning of period	298	278
Cash and cash equivalents at end of period	104	94
Noncash investing activities:
Accrued capital expenditures	61,044	19,162
Asset retirement obligation	$ 16,854	$ 6,477