Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 430,298	$ 229,396
Accounts receivable:
Trade, net	355,093	316,854
Due from affiliates	4,124	3,299
Income taxes receivable	1,394	7,447
Inventories	233,402	197,056
Prepaid expenses	13,337	13,438
Other current assets:
Derivatives Assets, Current	151,431	279,119
Other	7,335	3,746
Total current assets	1,196,414	1,050,355
Oil and gas properties, using the successful efforts method of accounting:
Proved properties	15,007,980	14,259,708
Unproved properties	218,404	231,555
Accumulated depletion, depreciation and amortization	(4,633,359)	(4,412,913)
Total property, plant and equipment	10,593,025	10,078,350
Goodwill	298,142	298,142
Other property and equipment, net	1,228,108	1,217,694
Other assets:
Investment in unconsolidated affiliate	216,369	204,129
Derivative Assets, Noncurrent	95,121	55,257
Other, net	134,118	165,103
Assets, Total	13,761,297	13,069,030
Accounts payable:
Trade	780,395	729,942
Due to affiliates	39,968	96,935
Interest payable	37,494	68,083
Income taxes payable	292	208
Deferred Tax Liabilities, Net, Current	51,783	86,481
Other current liabilities:
Derivative Liabilities, Current	20,413	13,416
Other	41,521	39,725
Total current liabilities	971,866	1,034,790
Long-term debt	3,017,280	3,721,193
Derivative Liabilities, Noncurrent	13,372	12,307
Deferred income taxes	2,202,637	2,140,416
Other liabilities	290,071	293,016
Stockholders' equity:
Common stock, $.01 par value; 500,000,000 shares authorized; 134,763,095 and 133,121,092 shares issued at June 30, 2012 and December 31, 2011, respectively	1,458	1,350
Additional paid-in capital	4,898,318	3,683,934
Treasury stock at cost: 11,727,359 and 11,264,936 at June 30, 2012 and December 31, 2011, respectively	(420,947)	(510,570)
Retained earnings	2,609,801	2,514,640
Total equity attributable to common stockholders	7,088,630	5,689,354
Noncontrolling interests in consolidating subsidiaries	177,441	177,954
Total equity	7,266,071	5,867,308
Commitments and contingencies
Liabilities and Stockholders' Equity, Total	$ 13,761,297	$ 13,069,030