Condensed Statements of Cash Flows (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net earnings	$ 52,669	$ 106,692
Depreciation, depletion and amortization	105,068	81,197
Gain on purchase	(1,046)
Amortization of debt issuance costs and net discount	4,205	4,218
Dry hole and impairment	298	1,428
Derivatives	19,496	(46,110)
Stock-based compensation expense	5,439	5,008
Deferred income taxes	19,572	61,142
Other, net	674
Cash paid for abandonment	(864)	(1,535)
Allowance for bad debt		(38,508)
Change in book overdraft	4,022	2,007
Changes in operating assets and liabilities:
Accounts receivable	(18,543)	(27,950)
Inventories, prepaid expenses, and other current assets	(1,813)	(5,226)
Accounts payable and revenue and royalties payable	24,044	(2,687)
Accrued interest and other accrued liabilities	(6,699)	(4,807)
Net cash provided by operating activities	206,522	134,869
Cash flows from investing activities:
Exploration and development of oil and gas properties	(271,433)	(135,038)
Property acquisitions	(145,461)	(150,674)
Capitalized interest	(18,664)	(13,054)
Net cash used in investing activities	(435,558)	(298,766)
Cash flows from financing activities:
Proceeds from issuances on line of credit	243,300	159,200
Repayments of borrowings under line of credit	(235,900)	(155,900)
Long-term borrowings under credit facility	357,500	165,000
Repayments of long-term borrowings under credit facility	(132,500)	(227,000)
Financing obligation	(185)	(169)
Debt issuance costs	(677)
Dividends paid	(8,124)	(8,083)
Proceeds from issuance of common stock, net		224,313
Proceeds from stock option exercises	3,415	1,156
Excess income tax benefit and other	2,177	308
Net cash provided by financing activities	229,006	158,825
Net decrease in cash and cash equivalents	(30)	(5,072)
Cash and cash equivalents at beginning of period	278	5,311
Cash and cash equivalents at end of period	248	239
Noncash investing activities:
(Decrease) increase in accrued capital expenditures	(32,781)	13,486
Increase in asset retirement obligation	$ 1,642	$ 1,860