Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK	CAPITAL SURPLUS	ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME	RETAINED EARNINGS
Balance at beginning of period, (in shares) at Dec. 31, 2015		131,156
Balance at beginning of period at Dec. 31, 2015		$ 131	$ 979,477	$ (10,294)	$ 34,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		1,039
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,405)
Repurchases of common stock		$ (4)			(178,780)
Stock-based compensation expense			42,699
Exercises of stock options, (in shares)	7	7
Exercises of stock options			223
Tax impact of equity incentive plans			13
Foreign currency translation adjustments, net of tax	$ (10,208)			(10,208)
Net income	343,389				343,389
Cash dividends ($1.12 per share, $.96 per share and $.88 per share)					(114,514)
Balance at end of period, (in shares) at Dec. 31, 2016		127,797
Balance at end of period at Dec. 31, 2016		$ 128	1,022,411	(20,502)	84,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		918
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,454)
Repurchases of common stock		$ (5)			(217,031)
Stock-based compensation expense			42,191
Foreign currency translation adjustments, net of tax	24,009			24,009
Net income	290,584				290,584
Cash dividends ($1.12 per share, $.96 per share and $.88 per share)					(121,082)
Balance at end of period, (in shares) at Dec. 31, 2017		124,261
Balance at end of period at Dec. 31, 2017	1,105,265	$ 124	1,064,601	3,507	37,033
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		666
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(5,849)
Repurchases of common stock		$ (6)			(364,862)
Stock-based compensation expense			44,953
Foreign currency translation adjustments, net of tax	(19,616)			(19,616)
Net income	434,288				434,288
Cash dividends ($1.12 per share, $.96 per share and $.88 per share)			(30,365)		(106,459)
Balance at end of period, (in shares) at Dec. 31, 2018		119,078
Balance at end of period at Dec. 31, 2018	$ 1,063,198	$ 119	$ 1,079,188	$ (16,109)	$ 0