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, 2014		135,134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		570
Repurchases of common stock, (in shares)		(672)
Exercises of stock options, (in shares)		40
Balance at end of period, (in shares) at Mar. 31, 2015		135,072
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		1	(1)
Repurchases of common stock		(1)			(40,351)
Stock-based compensation expense			8,843
Exercise of stock options			1,113
Tax impact of equity incentive plans			4,249
Foreign currency translation adjustments, net of tax	$ (19,962)			(19,962)
Net income	77,922				77,922
Cash dividends ($.22 per share and $.20 per share)					(27,048)
Balance at end of period at Mar. 31, 2015		$ 135	942,361	(5,232)	47,359
Balance at beginning of period, (in shares) at Dec. 31, 2015		131,156
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		901
Repurchases of common stock, (in shares)		(741)
Exercises of stock options, (in shares)		2
Balance at end of period, (in shares) at Mar. 31, 2016		131,318
Balance at beginning of period at Dec. 31, 2015	1,003,781	$ 131	979,477	(10,294)	34,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock		1	(1)
Repurchases of common stock		(1)			(31,366)
Stock-based compensation expense			10,348
Exercise of stock options			60
Tax impact of equity incentive plans			(459)
Foreign currency translation adjustments, net of tax	7,986			7,986
Net income	83,416				83,416
Cash dividends ($.22 per share and $.20 per share)					(28,812)
Balance at end of period at Mar. 31, 2016	$ 1,044,953	$ 131	$ 989,425	$ (2,308)	$ 57,705