Statement of Shareholders Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2008	$ 1,090,786	$ 346,832	$ 774,117	$ 15,577	$ (45,740)
Beginning Balance, Shares at Dec. 31, 2008		151,233
Stock options exercised	1,430	1,430
Stock options exercised, Shares	666
Employee stock plan grants	3,397		3,397
Employee stock plan grants, Shares	85
Shares re-issued from treasury	0	(1,430)	(33,785)		35,215
Net share settlements	(11,293)	0	(11,293)
Net share settlements, Shares	(225)
Fair value of employee stock plan grants	16,294	16,294
Tax benefit of stock options exercised	14,213	14,213
Comprehensive earnings:
Net earnings (loss)	(451,053)		(451,053)
Reclassification of derivative fair value into earnings, net of taxes	(15,577)			(15,577)
Total comprehensive earnings (loss)	(466,630)
Ending Balance at Dec. 31, 2009	648,197	377,339	281,383	0	(10,525)
Ending Balance, Shares at Dec. 31, 2009	151,759
Stock options exercised	6,561	6,561
Stock options exercised, Shares		1,206
Employee stock plan grants	4,841	4,841
Employee stock plan grants, Shares		105
Shares re-issued from treasury	0	(587)	(9,938)		10,525
Net share settlements	(23,707)		(23,707)
Net share settlements, Shares		(502)
Fair value of employee stock plan grants	21,103	21,103
Tax benefit of stock options exercised	17,522	17,522
Comprehensive earnings:
Net earnings (loss)	464,459		464,459
Ending Balance at Dec. 31, 2010	1,138,976	426,779	712,197		0
Ending Balance, Shares at Dec. 31, 2010		152,568
Stock options exercised	9,928	9,928
Stock options exercised, Shares		672
Employee stock plan grants	700	0
Employee stock plan grants, Shares		150
Shares re-issued from treasury	0	(686)	(4,531)		5,217
Shares repurchased	(20,868)				(20,868)
Shares repurchased, Shares		(588)
Net share settlements	(15,429)		(15,429)
Net share settlements, Shares		(325)
Fair value of employee stock plan grants	20,988	20,988
Tax benefit of stock options exercised	6,212	6,212
Comprehensive earnings:
Net earnings (loss)	453,202		453,202
Ending Balance at Dec. 31, 2011	$ 1,593,709	$ 463,221	$ 1,145,439	$ 0	$ (14,951)
Ending Balance, Shares at Dec. 31, 2011		152,477