Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
OPERATING ACTIVITIES:
Net income	$ 99,213	$ 33,137
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization	159,369	163,140
Impairment of oil and natural gas properties (Note 2)	0	115,874
Unrealized (gain) loss on derivatives	(9,561)	606
Deferred tax expense	57,817	23,409
Gain on disposition of assets	(3,399)	(1,239)
Stock compensation plans	10,654	7,978
Other, net	3,005	2,218
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(13,001)	1,675
Accounts payable	2,219	(28,587)
Material and supplies	(751)	(129)
Accrued liabilities	11,313	(2,151)
Other, net	1,010	(899)
Net cash provided by operating activities	317,888	315,032
INVESTING ACTIVITIES:
Capital expenditures	(339,300)	(371,703)
Producing property and other acquisitions	0	(2,193)
Proceeds from disposition of assets	16,829	6,288
Net cash used in investing activities	(322,471)	(367,608)
FINANCING ACTIVITIES:
Borrowings under credit agreement	183,900	250,500
Payments under credit agreement	(185,000)	(217,600)
Proceeds from exercise of stock options	81	89
Book overdrafts	5,669	19,837
Net cash provided by financing activities	4,650	52,826
Net increase in cash and cash equivalents	67	250
Cash and cash equivalents, beginning of period	974	835
Cash and cash equivalents, end of period	$ 1,041	$ 1,085