Statement of Shareholders Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2012	$ (577,867)	$ 474,016	$ (1,051,870)	$ (13)
Beginning Balance, Shares at Dec. 31, 2012		152,930,000
Stock options exercised	11	$ 11
Stock options exercised, Shares		1,000
Employee stock plan grants	700	$ 700		0
Shares re-issued from treasury	0	$ (711)	(652)	1,363
Shares repurchased	(3,311)			(3,311)
Shares repurchased, Shares		(165,000)
Net share settlements	(2,118)		(2,118)
Net share settlements, Shares		(122,000)
Fair value of employee stock plan grants	13,257	$ 13,257
Tax benefit of stock options exercised	0	0
Comprehensive earnings:
Net earnings (loss)	237,838		237,838
Ending Balance at Dec. 31, 2013	(331,490)	$ 487,273	(816,802)	(1,961)
Ending Balance, Shares at Dec. 31, 2013		152,991,000
Employee stock plan grants, Shares		347,000
Stock options exercised	770	$ 770
Stock options exercised, Shares		43,000
Employee stock plan grants	700	$ 700
Shares re-issued from treasury	0	$ (770)	(1,450)	2,220
Shares repurchased	(6,472)			(6,472)
Shares repurchased, Shares		(332,000)
Net share settlements	(2,639)		(2,639)
Net share settlements, Shares		(104,000)
Fair value of employee stock plan grants	7,940	$ 7,940
Comprehensive earnings:
Net earnings (loss)	542,851		542,851
Ending Balance at Dec. 31, 2014	211,660	$ 495,913	(278,040)	(6,213)
Ending Balance, Shares at Dec. 31, 2014		152,896,000
Employee stock plan grants, Shares		298,000
Stock options exercised	0	$ 0
Stock options exercised, Shares		0
Employee stock plan grants	700	$ 700
Shares re-issued from treasury	0	$ 0	(6,037)	6,037
Net share settlements	(2,514)		(2,514)
Net share settlements, Shares		(166,000)
Fair value of employee stock plan grants	5,437	$ 5,437
Comprehensive earnings:
Net earnings (loss)	(3,207,220)		(3,207,220)
Ending Balance at Dec. 31, 2015	$ (2,991,937)	$ 502,050	$ (3,493,811)	$ (176)
Ending Balance, Shares at Dec. 31, 2015		153,256,000
Employee stock plan grants, Shares		526,000