Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock
Balance at Dec. 31, 2009	$ 763,784	$ 493	$ 146,036	$ 598,493	$ 18,762
Balance (in shares) at Dec. 31, 2009		49,377
Increase (Decrease) in Stockholders' Equity
Net income	28,586			28,586
Translation adjustment, net of tax	(4,135)				(4,135)
Options exercised	17,948	7	17,941
Options exercised (in shares)		707
Stock-based compensation expense	3,577		3,577
Tax benefit of options exercised	(2,430)		(2,430)
Cash dividends declared on common stock, $0.625, $0.50 and $0.40 per share for the year ended December 31, 2012, 2011 and 2010, respectively	(19,838)			(19,838)
Common stock issued at $33.71, $30.91 and $26.42 per share for the year ended December 31, 2012, 2011 and 2010, respectively	301		301
Common stock issued (in shares)		12
Balance at Dec. 31, 2010	787,793	500	165,425	607,241	14,627
Balance (in shares) at Dec. 31, 2010		50,096
Increase (Decrease) in Stockholders' Equity
Net income	50,900			50,900
Translation adjustment, net of tax	(7,844)				(7,844)
Options exercised	214		214
Options exercised (in shares)		8
Stock-based compensation expense	6,194		6,194
Tax benefit of options exercised	(1,554)		(1,554)
Repurchase of common stock	(53,208)					(53,208)
Repurchase of common stock (in shares)		(1,948)
Retirement of common stock		(19)		(53,189)		53,208
Cash dividends declared on common stock, $0.625, $0.50 and $0.40 per share for the year ended December 31, 2012, 2011 and 2010, respectively	(24,336)			(24,336)
Common stock issued at $33.71, $30.91 and $26.42 per share for the year ended December 31, 2012, 2011 and 2010, respectively	204		204
Common stock issued (in shares)		7
Balance at Dec. 31, 2011	758,363	481	170,483	580,616	6,783
Balance (in shares) at Dec. 31, 2011	48,163	48,163
Increase (Decrease) in Stockholders' Equity
Net income	41,918			41,918
Pension adjustment net of tax	(243)				(243)
Translation adjustment, net of tax	5,559				5,559
Options exercised	4,925	2	4,923
Options exercised (in shares)		185
Stock-based compensation expense	10,195		10,195
Tax benefit of options exercised	(233)		(233)
Cash dividends declared on common stock, $0.625, $0.50 and $0.40 per share for the year ended December 31, 2012, 2011 and 2010, respectively	(30,225)			(30,225)
Shares issued from release of restricted stock units	(1,109)		(1,109)
Shares issued from release of restricted stock units (in shares)		62
Common stock issued at $33.71, $30.91 and $26.42 per share for the year ended December 31, 2012, 2011 and 2010, respectively	418		418
Common stock issued (in shares)		12
Balance at Dec. 31, 2012	$ 789,568	$ 483	$ 184,677	$ 592,309	$ 12,099
Balance (in shares) at Dec. 31, 2012	48,422	48,422