Condensed Consolidated Statement Of Stockholders' Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Beginning balance at Dec. 31, 2016	$ 550,269	$ 274	$ 185,981	$ 395,279	$ (1,798)	$ (29,467)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	115,420			115,420
Issuance of 190,753 shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(7,313)	2	(7,315)
Stock-based compensation expense	15,042		15,042
Issuance of 63,677 deferred stock units relating to prior year compensation	6,907		6,907
Other comprehensive income					4,077
Cash dividends ($1.50 per share)	(37,346)			(37,346)
Dividend equivalents on stock-based awards			1,199	(1,199)
Ending balance at Sep. 30, 2017	$ 647,056	$ 276	$ 201,814	$ 472,154	$ 2,279	$ (29,467)