Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK:	CAPITAL SURPLUS:	ACCUMULATED OTHER COMPREHENSIVE INCOME:	RETAINED EARNINGS:
Balance at beginning of period, (in shares) at Dec. 31, 2013		137,466
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		798
Repurchases of common stock, (in shares)		(1,557)
Exercises of stock options, (in shares)		394
Balance at end of period, (in shares) at Jun. 30, 2014		137,101
Balance at beginning of period at Dec. 31, 2013		$ 137	$ 868,120	$ 38,071	$ 13,315
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock		1	(1)
Repurchases of common stock		(1)			(65,157)
Balance at end of period at Jun. 30, 2014		$ 137	899,631	40,357	35,436
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense			19,149
Exercise of stock options			10,628
Tax impact of equity incentive plans			1,735
Foreign currency translation adjustments, net of tax	$ 2,286			2,286
Net income	136,691				136,691
Cash dividends					(49,413)
Balance at beginning of period, (in shares) at Dec. 31, 2014		135,134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		593
Repurchases of common stock, (in shares)		(1,575)
Exercises of stock options, (in shares)		48
Balance at end of period, (in shares) at Jun. 30, 2015		134,200
Balance at beginning of period at Dec. 31, 2014	979,858	$ 135	928,157	14,730	36,836
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock		1	(1)
Repurchases of common stock		(2)			(90,892)
Balance at end of period at Jun. 30, 2015	1,014,675	$ 134	953,802	1,151	59,588
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense			19,688
Exercise of stock options			1,334
Tax impact of equity incentive plans			$ 4,624
Foreign currency translation adjustments, net of tax	(13,579)			$ (13,579)
Net income	$ 167,628				167,628
Cash dividends					$ (53,984)