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)	193,397					193,397	193,397
Hedge derivative contract settlements reclassified into earnings from AOCI, net of income tax					(37,181)		(37,181)
Foreign currency translation adjustment	(933)				(933)		(933)
Issuance and vesting of stock compensation		47	14,421	(1,472)			12,996
Balances at Sep. 30, 2013		1,837	765,815	(50,967)	123,379	(1,804,582)	(964,518)
Balances at Dec. 31, 2013		1,840	770,092	(51,422)	109,881	(1,836,361)	(1,005,970)
Net income (loss)	(71,171)					(71,171)	(71,171)
Hedge derivative contract settlements reclassified into earnings from AOCI, net of income tax					(20,939)		(20,939)
Foreign currency translation adjustment	(6,162)				(6,162)		(6,162)
Issuance and vesting of stock compensation		32	9,114	(2,388)			6,758
Balances at Sep. 30, 2014		$ 1,872	$ 779,206	$ (53,810)	$ 82,780	$ (1,907,532)	$ (1,097,484)