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, 2012	$ 789,568	$ 483	$ 184,677	$ 592,309	$ 12,099
Balance (in shares) at Dec. 31, 2012		48,422
Increase (Decrease) in Stockholders' Equity
Net income	43,303			43,303
Translation adjustment, net of tax	1,449				1,449
Stock options exercised	5,333	2	5,331
Stock options exercised (in shares)		194
Stock-based compensation	8,656		8,656
Tax effect of options exercised	(2,187)		(2,187)
Shares issued from release of Restricted Stock Units	(2,072)	2	(2,074)
Shares issued from release of Restricted Stock Units (in shares)		111
Repurchase of common stock	(9,825)					(9,825)
Repurchase of common stock (in shares)		(342)
Cash dividends declared on common stock, $0.405, $0.125, and $0.25 per share for the period ended September 30, 2014, December 31, 2013, and September 30, 2013 respectively	(12,083)			(12,083)
Common stock issued at $35.87, $0, and $33.81 per share for stock bonus for the period ended September 30, 2014, December 31, 2013, and September 30, 2013, respectively	318		318
Common stock issued (in shares)		9
Balance at Sep. 30, 2013	822,460	487	194,721	623,529	13,548	(9,825)
Balance (in shares) at Sep. 30, 2013		48,394
Increase (Decrease) in Stockholders' Equity
Net income	7,668			7,668
Translation adjustment, net of tax	4,492				4,492
Pension adjustment, net of tax	46				46
Stock options exercised	9,724	3	9,721
Stock options exercised (in shares)		318
Stock-based compensation	3,434		3,434
Tax effect of options exercised	(458)		(458)
Retirement of treasury stock		(4)		(9,821)		9,825
Cash dividends declared on common stock, $0.405, $0.125, and $0.25 per share for the period ended September 30, 2014, December 31, 2013, and September 30, 2013 respectively	(6,087)			(6,087)
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	53,151			53,151
Translation adjustment, net of tax	(17,091)				(17,091)
Stock options exercised	4,178	2	4,176
Stock options exercised (in shares)		144
Stock-based compensation	8,789		8,789
Tax effect of options exercised	(275)		(275)
Shares issued from release of Restricted Stock Units	(3,497)	2	(3,499)
Shares issued from release of Restricted Stock Units (in shares)		176
Repurchase of common stock	(2,981)					(2,981)
Repurchase of common stock (in shares)		(95)
Cash dividends declared on common stock, $0.405, $0.125, and $0.25 per share for the period ended September 30, 2014, December 31, 2013, and September 30, 2013 respectively	(19,832)			(19,832)
Common stock issued at $35.87, $0, and $33.81 per share for stock bonus for the period ended September 30, 2014, December 31, 2013, and September 30, 2013, respectively	402		402
Common stock issued (in shares)		11
Balance at Sep. 30, 2014	$ 864,123	$ 490	$ 217,011	$ 648,608	$ 995	$ (2,981)
Balance (in shares) at Sep. 30, 2014		48,948