Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at January 1, 2012 at Dec. 31, 2011	$ 945	$ 477,204	$ 789	$ 34,983	$ (16,075)	$ 497,846
Net income				60,032		60,032
Employee stock options, restricted stock and employee stock purchase plan	12	1,088			(402)	698
Stock-based compensation expense		7,103				7,103
Income tax effect, net, of employee stock related activity		(433)				(433)
Treasury shares purchased at cost					(50,145)	(50,145)
Foreign currency translation			(1,523)			(1,523)
Balance at December 31 at Dec. 31, 2012	957	484,962	(734)	95,015	(66,622)	513,578
Net income				65,323		65,323
Employee stock options, restricted stock and employee stock purchase plan	23	8,284			(2,120)	6,187
Stock-based compensation expense		9,699				9,699
Income tax effect, net, of employee stock related activity		1,730				1,730
Treasury shares purchased at cost					(6,713)	(6,713)
Foreign currency translation			(8,750)			(8,750)
Balance at December 31 at Dec. 31, 2013	980	504,675	(9,484)	160,338	(75,455)	581,054
Net income				102,278		102,278
Employee stock options, restricted stock and employee stock purchase plan	12	2,970			(1,335)	1,647
Stock-based compensation expense		12,411				12,411
Income tax effect, net, of employee stock related activity		1,172				1,172
Treasury shares purchased at cost					(50,596)	(50,596)
Foreign currency translation			(22,508)			(22,508)
Balance at December 31 at Dec. 31, 2014	$ 992	$ 521,228	$ (31,992)	$ 262,616	$ (127,386)	$ 625,458