Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	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		48,712,000
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)		144,000
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)		176,000
Repurchase of common stock	(2,981)					$ (2,981)
Repurchase of common stock (in shares)		(95,000)
Cash dividends declared on common stock, $0.460, $0.14, and $0.405 for the period ended September 30, 2015, December 31, 2014 and September 30, 2014, respectively	(19,832)			(19,832)
Common stock issued at $34.32, $0, $35.87 per share for stock bonus for the period ended September 30, 2015, December 31, 2014 and September 30, 2014	402		402
Common stock issued (in shares)		11,000
Balance at Sep. 30, 2014	864,123	$ 490	217,011	648,608	995	(2,981)
Balance (in shares) at Sep. 30, 2014		48,948,000
Increase (Decrease) in Stockholders' Equity
Net income	10,380			10,380
Translation adjustment, net of tax	(7,805)				(7,805)
Pension adjustment, net of tax	(370)				(370)
Stock options exercised	404	$ 0	404
Stock options exercised (in shares)		17,000
Stock-based compensation	3,565		3,565
Tax effect of options exercised	7		7
Shares issued from release of Restricted Stock Units	(5)	$ 0	(5)
Shares issued from release of Restricted Stock Units (in shares)		1,000
Retirement of common stock	0	$ (1)		(2,980)		2,981
Cash dividends declared on common stock, $0.460, $0.14, and $0.405 for the period ended September 30, 2015, December 31, 2014 and September 30, 2014, respectively	(6,834)			(6,834)
Balance at Dec. 31, 2014	863,465	$ 489	220,982	649,174	(7,180)
Balance (in shares) at Dec. 31, 2014		48,966,000
Increase (Decrease) in Stockholders' Equity
Net income	53,156			53,156
Translation adjustment, net of tax	(14,864)				(14,864)
Stock options exercised	7,019	$ 2	7,017
Stock options exercised (in shares)		239,000
Stock-based compensation	8,744		8,744
Tax effect of options exercised	(244)		(244)
Shares issued from release of Restricted Stock Units	(3,646)	$ 2	(3,648)
Shares issued from release of Restricted Stock Units (in shares)		205,000
Repurchase of common stock	$ (47,144)		(7,615)			(39,529)
Repurchase of common stock (in shares)	(1,148,410)	(1,149,000)
Cash dividends declared on common stock, $0.460, $0.14, and $0.405 for the period ended September 30, 2015, December 31, 2014 and September 30, 2014, respectively	$ (22,657)			(22,657)
Common stock issued at $34.32, $0, $35.87 per share for stock bonus for the period ended September 30, 2015, December 31, 2014 and September 30, 2014	552		552
Common stock issued (in shares)		16,000
Balance at Sep. 30, 2015	$ 844,381	$ 493	$ 225,788	$ 679,673	$ (22,044)	$ (39,529)
Balance (in shares) at Sep. 30, 2015		48,277,000