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	4,795			4,795
Translation adjustment, net of tax	(5,817)				(5,817)
Stock options exercised	496	1	495
Stock options exercised (in shares)		18
Stock-based compensation	2,813		2,813
Tax effect of options exercised	(1,843)		(1,843)
Shares issued from release of Restricted Stock Units	(1,906)	1	(1,907)
Shares issued from release of Restricted Stock Units (in shares)		108
Common stock issued at $35.87, $31.58 and $33.83 per share for stock bonus for the period ended March 31, 2014, December 31, 2013 and March 31, 2013 respectively	315		315
Common stock issued (in shares)		9
Balance at Mar. 31, 2013	788,421	485	184,550	597,104	6,282
Balance (in shares) at Mar. 31, 2013		48,557
Increase (Decrease) in Stockholders' Equity
Net income	46,176			46,176
Translation adjustment, net of tax	11,758				11,758
Pension adjustment, net of tax	46				46
Stock options exercised	14,561	4	14,557
Stock options exercised (in shares)		494
Stock-based compensation	9,277		9,277
Tax effect of options exercised	(802)		(802)
Shares issued from release of Restricted Stock Units	(166)	1	(167)
Shares issued from release of Restricted Stock Units (in shares)		3
Repurchase of common stock	(9,825)					(9,825)
Repurchase of common stock (in shares)		(342)
Retirement of treasury stock		(4)		(9,821)		9,825
Cash dividends declared on common stock, $0.125 and $0.375 per share for the period ended March 31, 2014 and December 31, 2013 respectively	(18,170)			(18,170)
Common stock issued at $35.87, $31.58 and $33.83 per share for stock bonus for the period ended March 31, 2014, December 31, 2013 and March 31, 2013 respectively	3		3
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, $0.125 and $0.375 per share for the period ended March 31, 2014 and December 31, 2013 respectively	(6,116)			(6,116)
Common stock issued at $35.87, $31.58 and $33.83 per share for stock bonus for the period ended March 31, 2014, December 31, 2013 and March 31, 2013 respectively	402		402
Common stock issued (in shares)		11
Balance at Mar. 31, 2014	$ 847,509	$ 489	$ 208,870	$ 621,260	$ 16,890
Balance (in shares) at Mar. 31, 2014		48,938