Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net earnings	$ 114,914	$ 52,669
Depreciation, depletion and amortization	100,903	105,068
Gain (Loss) on Sale of Property Plant Equipment	1,600	0
Gain on purchase	0	(1,046)
Extinguishment of debt	6,842	0
Amortization of debt issuance costs and net discount	3,688	4,205
Impairment of oil and natural gas properties	66	0
Dry hole and impairment	211	298
Derivatives	(66,901)	19,496
Stock-based compensation expense	5,426	5,439
Deferred income taxes	66,782	19,572
Other, net	(524)	(190)
Allowance for bad debt	315	0
Change in book overdraft	(2,628)	4,022
Changes in operating assets and liabilities:
Accounts receivable	9,063	(18,543)
Inventories, prepaid expenses, and other current assets	(4,702)	(1,813)
Accounts payable and revenue and royalties payable	7,755	24,044
Accrued interest and other accrued liabilities	8,457	(6,699)
Net Cash Provided by (Used in) Operating Activities	248,067	206,522
Cash flows from investing activities:
Exploration and development of oil and natural gas properties	(328,968)	(271,433)
Property acquisitions	(24,851)	(145,461)
Capitalized interest	(9,723)	(18,664)
Proceeds from sale of assets	15,722	0
Deposits on asset sales	(3,300)	0
Net cash used in investing activities	(351,120)	(435,558)
Cash flows from financing activities:
Proceeds from issuances on line of credit	0	243,300
Payments on borrowings under line of credit	0	(235,900)
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)	0
Long-term borrowings under credit facility	858,700	357,500
Repayments of long-term borrowings under credit facility	(989,700)	(132,500)
Financing obligation	(202)	(185)
Debt issuance costs	(11,424)	(677)
Dividends paid	(8,771)	(8,124)
Stock options and restricted stock issued	3,497	3,415
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	735	2,177
Net cash provided by financing activities	102,836	229,006
Net decrease in cash and cash equivalents	(217)	(30)
Cash and cash equivalents at beginning of period	298	278
Cash and cash equivalents at end of period	81	248
Noncash investing activities:
Accrued capital expenditures	55,311	20,809
Asset retirement obligation	$ 15,012	$ 1,642