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, 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)
Balances at Dec. 31, 2014		1,878	781,669	(53,810)	71,853	(1,939,461)	(1,137,871)
Net income (loss)	(471,718)					(471,718)	(471,718)
Hedge derivative contract settlements reclassified into earnings from AOCI, net of income tax					(17,553)		(17,553)
Foreign currency translation adjustment	$ (5,996)				(5,996)		(5,996)
Issuance and vesting of stock compensation		37	5,114	(115)			5,036
Balances at Sep. 30, 2015		$ 1,915	$ 786,783	$ (53,925)	$ 48,304	$ (2,411,179)	$ (1,628,102)