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	23,297			23,297
Translation adjustment, net of tax	(6,815)				(6,815)
Stock options exercised	776	1	775
Stock options exercised (in shares)		31
Stock-based compensation	5,649		5,649
Tax effect of options exercised	(1,850)		(1,850)
Shares issued from release of Restricted Stock Units	(2,019)	1	(2,020)
Shares issued from release of Restricted Stock Units (in shares)		107
Repurchase of common stock	(9,825)					(9,825)
Repurchase of common stock (in shares)		(342)
Cash dividends declared on common stock, $0.265, $0.25, and $0.125 per share for the period ended June 30, 2014, December 31, 2013, and June 30, 2013 respectively	(6,068)			(6,068)
Common stock issued at $35.87, $0, and $33.81 per share for stock bonus for the period ended June 30, 2014, December 31, 2013, and June 30, 2013, respectively	318		318
Common stock issued (in shares)		9
Balance at Jun. 30, 2013	793,031	485	187,549	609,538	5,284	(9,825)
Balance (in shares) at Jun. 30, 2013		48,227
Increase (Decrease) in Stockholders' Equity
Net income	27,674			27,674
Translation adjustment, net of tax	12,756				12,756
Pension adjustment, net of tax	46				46
Stock options exercised	14,281	4	14,277
Stock options exercised (in shares)		481
Stock-based compensation	6,441		6,441
Tax effect of options exercised	(795)		(795)
Shares issued from release of Restricted Stock Units	(53)	1	(54)
Shares issued from release of Restricted Stock Units (in shares)		4
Retirement of treasury stock		(4)		(9,821)		9,825
Cash dividends declared on common stock, $0.265, $0.25, and $0.125 per share for the period ended June 30, 2014, December 31, 2013, and June 30, 2013 respectively	(12,102)			(12,102)
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	32,538			32,538
Translation adjustment, net of tax	(1,194)				(1,194)
Stock options exercised	2,626	1	2,625
Stock options exercised (in shares)		92
Stock-based compensation	5,691		5,691
Tax effect of options exercised	(186)		(186)
Shares issued from release of Restricted Stock Units	(2,911)	2	(2,913)
Shares issued from release of Restricted Stock Units (in shares)		158
Cash dividends declared on common stock, $0.265, $0.25, and $0.125 per share for the period ended June 30, 2014, December 31, 2013, and June 30, 2013 respectively	(12,969)			(12,969)
Common stock issued at $35.87, $0, and $33.81 per share for stock bonus for the period ended June 30, 2014, December 31, 2013, and June 30, 2013, respectively	402		402
Common stock issued (in shares)		11
Balance at Jun. 30, 2014	$ 865,276	$ 489	$ 213,037	$ 634,858	$ 16,892	$ 0
Balance (in shares) at Jun. 30, 2014		48,973