Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2010	$ 880,017	$ 424	$ 706,857	$ (9,778)	$ 182,652	$ (138)
Stock issued for benefit plans	1,612		791	821
Stock options exercised	1,151	1	1,150
Purchase of treasury shares	(3,393)			(3,393)
Tax benefits from stock-based compensation	333		333
Employee stock purchase plan	1,000	1	999
Issuance of restricted stock		4	(4)
Amortization of share-based compensation	16,830		16,830
Net Income (Loss)	98,821				98,821
Other comprehensive income	138					138
Ending Balance at Dec. 31, 2011	996,509	430	726,956	(12,350)	281,473
Stock issued for benefit plans	1,654		354	1,300
Stock options exercised	636	1	635
Purchase of treasury shares	(2,805)			(2,805)
Tax benefits from stock-based compensation	175		175
Employee stock purchase plan	1,076		1,076
Issuance of restricted stock		4	(4)
Amortization of share-based compensation	18,676		18,676
Net Income (Loss)	20,939				20,939
Other comprehensive income	0
Ending Balance at Dec. 31, 2012	1,036,860	435	747,868	(13,855)	302,412
Stock issued for benefit plans	1,622		(1,171)	2,793
Stock options exercised	4		4
Purchase of treasury shares	(1,513)			(1,513)
Tax benefits from stock-based compensation	(1,607)		(1,607)
Employee stock purchase plan	946	1	945
Issuance of restricted stock		3	(3)
Amortization of share-based compensation	15,936		15,936
Net Income (Loss)	(19,032)				(19,032)
Other comprehensive income	0
Ending Balance at Dec. 31, 2013	$ 1,033,216	$ 439	$ 761,972	$ (12,575)	$ 283,380