Consolidated Statement of Stockholders' Equity - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
BALANCE (in shares) at Dec. 31, 2017		25,515
BALANCE at Dec. 31, 2017	$ 1,124,282	$ 255	$ 291,461	$ 1,246,323	$ (123,226)	$ (290,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	92,277			92,277
Other comprehensive income, net	(3,132)				(3,132)
Purchases of treasury stock	(51,276)					(51,276)
Net issuance of treasury shares to employee stock compensation plans (in shares)		(3)
Net issuance of treasury shares to employee stock compensation plans	12		(12,833)			12,845
Stock-based compensation	9,864		9,864
Cash dividends, net of estimated forfeitures relative to participating securities	(10,812)			(10,812)
BALANCE (in shares) at Jun. 30, 2018		25,512
BALANCE at Jun. 30, 2018	1,172,612	$ 255	$ 288,492	1,339,185	$ (126,358)	$ (328,962)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of ASC 606 cumulative adjustment	$ 11,397			$ 11,397