Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK	CAPITAL SURPLUS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	RETAINED EARNINGS
Balance at beginning of period, (in shares) at Dec. 31, 2014		135,134
Balance at beginning of period at Dec. 31, 2014		$ 135	$ 928,157	$ 14,730	$ 36,836
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		785
Net issuances of restricted stock		$ 1	(1)
Repurchases of common stock, (in shares)		(4,817)
Repurchases of common stock		$ (5)			(252,916)
Stock-based compensation expense			41,292
Exercises of stock options, (in shares)	54	54
Exercises of stock options		$ 0	1,529
Tax impact of equity incentive plans			8,500
Foreign currency translation adjustments, net of tax	$ (25,024)			(25,024)
Net income	$ 357,796				357,796
Cash dividends					(107,249)
Balance at end of period, (in shares) at Dec. 31, 2015		131,156
Balance at end 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		$ 0	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					(114,514)
Balance at end of period, (in shares) at Dec. 31, 2016		127,797
Balance at end of period at Dec. 31, 2016	$ 1,086,599	$ 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
Exercises of stock options, (in shares)	0	0
Exercises of stock options		$ 0	0
Tax impact of equity incentive plans			0
Foreign currency translation adjustments, net of tax	$ 24,009			24,009
Net income	290,584				290,584
Cash dividends					(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