Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net earnings (loss)	$ 33,898	$ (52,497)
Depreciation, depletion and amortization	48,422	52,610
Gain on sale of assets	(1,763)	0
Gain on purchase	0	(1,046)
Amortization of debt issuance costs and net discount	2,037	2,099
Dry hole and impairment	28	0
Derivatives	42,837	124,459
Stock-based compensation expense	3,104	3,052
Deferred income taxes	16,567	(44,321)
Other, net	683	576
Allowance for bad debt	315	0
Change in book overdraft	(509)	4,736
Changes in operating assets and liabilities:
Accounts receivable	(7,835)	(16,330)
Inventories, prepaid expenses, and other current assets	(2,686)	1,662
Accounts payable and revenue and royalties payable	(674)	6,577
Accrued interest and other accrued liabilities	20,982	18,857
Net cash provided by operating activities	155,406	100,434
Cash flows from investing activities:
Exploration and development of oil and natural gas properties	(167,758)	(130,672)
Property acquisitions	(8,529)	(2,413)
Capitalized interest	(5,190)	(10,392)
Proceeds from sale of assets	15,700	0
Deposits on asset sales	(3,300)	0
Net cash used in investing activities	(169,077)	(143,477)
Cash flows from financing activities:
Proceeds from issuances on line of credit	0	124,100
Payments on borrowings under line of credit	0	(115,900)
Proceeds from issuance of 6.375% Senior notes due 2022	600,000	0
Long-term borrowings under credit facility	102,700	63,500
Repayments of long-term borrowings under credit facility	(634,200)	(28,500)
Financing obligation	(101)	(92)
Debt issuance costs	(10,569)	(4)
Dividends paid	(4,381)	(4,060)
Stock options and restricted stock issued	3,498	1,573
Excess income tax benefit	422	2,228
Net cash provided by financing activities	57,369	42,845
Net increase (decrease) in cash and cash equivalents	43,698	(198)
Cash and cash equivalents at beginning of period	298	278
Cash and cash equivalents at end of period	43,996	80
Noncash investing activities:
Accrued capital expenditures	41,339	28,623
Asset retirement obligation	$ 4,994	$ 917