Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - 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, 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		$ 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
Exercises of stock options—excess over par value			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 ($.24 per share and $.22 per share)					(28,812)
Balance at end of period at Mar. 31, 2016		$ 131	989,425	(2,308)	57,705
Balance at beginning of period, (in shares) at Dec. 31, 2016		127,797
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuances of restricted stock, (in shares)		807
Repurchases of common stock, (in shares)		(1,425)
Exercises of stock options, (in shares)		0
Balance at end of period, (in shares) at Mar. 31, 2017		127,179
Balance at beginning 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		1	(1)
Repurchases of common stock		(2)			(68,295)
Stock-based compensation expense			9,857
Exercises of stock options—excess over par value			0
Tax impact of equity incentive plans			0
Foreign currency translation adjustments, net of tax	4,864			4,864
Net income	78,521				78,521
Cash dividends ($.24 per share and $.22 per share)					(30,601)
Balance at end of period at Mar. 31, 2017	$ 1,080,943	$ 127	$ 1,032,267	$ (15,638)	$ 64,187