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 (Scenario, Previously Reported [Member])	$ 880,017	$ 424	$ 706,857	$ (9,778)	$ 182,652	$ (138)
Beginning Balance (Restatement Adjustment [Member])	17,051	0	0	0	17,051	0
Beginning Balance at Dec. 31, 2010	897,068	424	706,857	(9,778)	199,703	(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	17,160		17,160
Net Income (Loss)	96,282				96,282
Net Income (Loss) at Jan. 01, 2011 (Scenario, Previously Reported [Member])	98,821
Net Income (Loss) (Restatement Adjustment [Member])	(2,539)
Other comprehensive income	138					138
Ending Balance at Dec. 31, 2011	1,011,351	430	727,286	(12,350)	295,985
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	18,995		18,995
Net Income (Loss)	21,701				21,701
Net Income (Loss) at Jan. 01, 2012 (Scenario, Previously Reported [Member])	20,939
Net Income (Loss) (Restatement Adjustment [Member])	762
Other comprehensive income	0
Ending Balance at Dec. 31, 2012	1,052,783	435	748,517	(13,855)	317,686
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	15,557		15,557
Net Income (Loss)	(2,442)				(2,442)
Net Income (Loss) at Jan. 01, 2013 (Scenario, Previously Reported [Member])	(19,032)
Net Income (Loss) (Restatement Adjustment [Member])	16,590
Other comprehensive income	0
Ending Balance at Dec. 31, 2013	$ 1,065,350	$ 439	$ 762,242	$ (12,575)	$ 315,244