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)		796
Repurchases of common stock, (in shares)		(2,808)
Exercises of stock options, (in shares)		469
Balance at end of period, (in shares) at Sep. 30, 2014		135,923
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		(3)			(126,828)
Balance at end of period at Sep. 30, 2014		136	912,978	25,076	34,393
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense			29,960
Exercise of stock options		$ 1	12,686
Tax impact of equity incentive plans			2,213
Foreign currency translation adjustments, net of tax	$ (12,995)			(12,995)
Net income	221,875				221,875
Cash dividends ($.60 per share and $.54 per share)					(73,969)
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)		591
Repurchases of common stock, (in shares)		(3,127)
Exercises of stock options, (in shares)		54
Balance at end of period, (in shares) at Sep. 30, 2015		132,652
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		(3)			(172,736)
Balance at end of period at Sep. 30, 2015	1,006,476	133	964,841	(6,227)	47,729
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense			30,540
Exercise of stock options		$ 0	1,511
Tax impact of equity incentive plans			$ 4,634
Foreign currency translation adjustments, net of tax	(20,957)			$ (20,957)
Net income	$ 264,353				264,353
Cash dividends ($.60 per share and $.54 per share)					$ (80,724)