Condensed Consolidated Statements Of Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Stockholders' Equity, Total [Member]
Balances at Dec. 31, 2012		$ 1,790	$ 751,394	$ (49,495)	$ 161,493	$ (1,997,979)	$ (1,132,797)
Net income (loss)	182,818					182,818	182,818
Hedge derivative contract settlements reclassified into earnings from AOCI, net of income tax					(26,042)		(26,042)
Foreign currency translation adjustment	(3,278)				(3,278)		(3,278)
Issuance and vesting of stock compensation		38	11,894	(1,125)			10,807
Balances at Jun. 30, 2013		1,828	763,288	(50,620)	132,173	(1,815,161)	(968,492)
Balances at Dec. 31, 2013		1,840	770,092	(51,422)	109,881	(1,836,361)	(1,005,970)
Net income (loss)	(94,928)					(94,928)	(94,928)
Hedge derivative contract settlements reclassified into earnings from AOCI, net of income tax					(12,971)		(12,971)
Foreign currency translation adjustment	759				759		759
Issuance and vesting of stock compensation		8	5,569	(2,383)			3,194
Balances at Jun. 30, 2014		$ 1,848	$ 775,661	$ (53,805)	$ 97,669	$ (1,931,289)	$ (1,109,916)