Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2011	$ 925,244	$ 402	$ 162,505	$ 780,780	$ (18,443)
Foreign currency translation adjustment	4,613				4,613
Net income	119,209			119,209
Comprehensive income	123,822
Options exercised and awards vested	10,809	3	10,806
Stock-based compensation	5,748		5,748
Excess tax benefits-stock options and awards	809		809
Balance at Dec. 31, 2012	1,066,432	405	179,868	899,989	(13,830)
Foreign currency translation adjustment	(6,340)				(6,340)
Net income	169,827			169,827
Comprehensive income	163,487
Options exercised and awards vested	10,506	3	10,503
Stock-based compensation	8,900		8,900
Excess tax benefits-stock options and awards	2,695		2,695
Treasury stock	(10,002)	(1)	(10,001)
Balance at Dec. 31, 2013	1,242,018	407	191,965	1,069,816	(20,170)
Foreign currency translation adjustment	(30,034)				(30,034)
Net income	208,712			208,712
Comprehensive income	178,678
Options exercised and awards vested	2,849	1	2,848
Stock-based compensation	11,856		11,856
Excess tax benefits-stock options and awards	25		25
Treasury stock	(190,234)	(20)	(190,214)
Balance at Dec. 31, 2014	$ 1,245,192	$ 388	$ 16,480	$ 1,278,528	$ (50,204)