Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Dec. 31, 2014		41,181
Beginning Balance at Dec. 31, 2014	$ 1,102,746	$ 412	$ 393,174	$ 789,428	$ (80,268)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66,053			66,053
Other comprehensive income (loss):
Cumulative translation adjustment	(28,727)				(28,727)
Issuance of common stock in connection with:
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017 (in shares)		713
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017	19,026	$ 7	19,019
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017 (in shares)		105
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017	(4,371)	$ 1	(4,372)
Stock units issued under incentive compensation plan	2,124		2,124
Purchase and retirement of common stock (in shares)		(765)
Purchase and retirement of common stock	(26,532)	$ (8)	(26,524)
Share-based compensation	17,284		17,284
Ending Balance (in shares) at Dec. 31, 2015		41,234
Ending Balance at Dec. 31, 2015	1,147,603	$ 412	400,705	855,481	(108,995)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85,520			85,520
Other comprehensive income (loss):
Cumulative translation adjustment	(41,884)				(41,884)
Issuance of common stock in connection with:
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017 (in shares)		820
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017	25,242	$ 8	25,234
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017 (in shares)		520
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017	(5,536)	$ 5	(5,541)
Stock units issued under incentive compensation plan	1,842		1,842
Purchase and retirement of common stock (in shares)		(537)
Purchase and retirement of common stock	(21,489)	$ (5)	(21,484)
Share-based compensation	$ 16,060		16,060
Ending Balance (in shares) at Dec. 31, 2016	42,037	42,037
Ending Balance at Dec. 31, 2016	$ 1,207,358	$ 420	416,816	941,001	(150,879)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	107,962			107,962
Other comprehensive income (loss):
Cumulative translation adjustment	$ 30,664				30,664
Issuance of common stock in connection with:
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017 (in shares)	123	123
Exercise of options, net of income tax benefit from share-based awards of $2,050 in 2015, $2,051 in 2016, $0 in 2017	$ 4,133	$ 1	4,132
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017 (in shares)		243
Restricted share grants, less net settled shares of 116 in 2015, 137 in 2016 and 92 in 2017	(4,440)	$ 2	(4,442)
Stock units issued under incentive compensation plan	1,547		1,547
Purchase and retirement of common stock (in shares)		(4,674)
Purchase and retirement of common stock	(168,094)	$ (46)	(168,048)
Cumulative effect due to adoption of new accounting standard	(3,189)			(3,189)
Share-based compensation	$ 16,030		16,030
Ending Balance (in shares) at Dec. 31, 2017	37,729	37,729
Ending Balance at Dec. 31, 2017	$ 1,191,971	$ 377	$ 266,035	$ 1,045,774	$ (120,215)