Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Dec. 31, 2013	$ 841,279	$ 486	$ 207,418	$ 615,289	$ 18,086
Balance (in shares) at Dec. 31, 2013		48,712
Increase (Decrease) in Stockholders' Equity
Net income	12,087			12,087
Translation adjustment, net of tax	(1,196)				(1,196)
Stock options exercised	1,769	1	1,768
Stock options exercised (in shares)		62
Stock-based compensation	2,379		2,379
Tax effect of options exercised	(135)		(135)
Shares issued from release of Restricted Stock Units	(2,960)	2	(2,962)
Shares issued from release of Restricted Stock Units (in shares)		153
Cash dividends declared on common stock, $0.140, $0.420, and $0.125 per share for the period ended March 31, 2015, December 31, 2014, and March 31, 2014 respectively	(6,116)			(6,116)
Common stock issued at $34.32, $0, and $35.87 per share for stock bonus for the period ended March 31, 2015, December 31, 2014, and March 31, 2014, respectively	402		402
Common stock issued (in shares)		11
Balance at Mar. 31, 2014	847,509	489	208,870	621,260	16,890	0
Balance (in shares) at Mar. 31, 2014		48,938
Increase (Decrease) in Stockholders' Equity
Net income	51,444			51,444
Translation adjustment, net of tax	(23,700)				(23,700)
Pension adjustment, net of tax	(370)				(370)
Stock options exercised	2,813	1	2,812
Stock options exercised (in shares)		99
Stock-based compensation	9,975		9,975
Tax effect of options exercised	(133)		(133)
Shares issued from release of Restricted Stock Units	(542)	0	(542)
Shares issued from release of Restricted Stock Units (in shares)		24
Repurchase of common stock (in shares)		(95)
Repurchase of common stock	(2,981)					(2,981)
Retirement of common stock		(1)		(2,980)		2,981
Cash dividends declared on common stock, $0.140, $0.420, and $0.125 per share for the period ended March 31, 2015, December 31, 2014, and March 31, 2014 respectively	(20,550)			(20,550)
Balance at Dec. 31, 2014	863,465	489	220,982	649,174	(7,180)
Balance (in shares) at Dec. 31, 2014		48,966
Increase (Decrease) in Stockholders' Equity
Net income	10,051			10,051
Translation adjustment, net of tax	(16,328)				(16,328)
Stock options exercised	5,484	2	5,482
Stock options exercised (in shares)		187
Stock-based compensation	2,784		2,784
Tax effect of options exercised	(184)		(184)
Shares issued from release of Restricted Stock Units	(3,607)	2	(3,609)
Shares issued from release of Restricted Stock Units (in shares)		191
Cash dividends declared on common stock, $0.140, $0.420, and $0.125 per share for the period ended March 31, 2015, December 31, 2014, and March 31, 2014 respectively	(6,927)			(6,927)
Common stock issued at $34.32, $0, and $35.87 per share for stock bonus for the period ended March 31, 2015, December 31, 2014, and March 31, 2014, respectively	552		552
Common stock issued (in shares)		16
Balance at Mar. 31, 2015	$ 855,290	$ 493	$ 226,007	$ 652,298	$ (23,508)	$ 0
Balance (in shares) at Mar. 31, 2015		49,360