Condensed Consolidated Statement Of Stockholders' Equity - 6 months ended Jun. 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	83,282			83,282
Issuance of 176,272 shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(7,543)	2	(7,545)
Stock-based compensation expense	9,312		9,312
Issuance of 63,677 deferred stock units relating to prior year compensation	6,907		6,907
Other comprehensive income					2,415
Cash dividends ($1.00 per share)	(24,887)			(24,887)
Dividend equivalents on stock-based awards			797	(797)
Ending balance at Jun. 30, 2017	$ 619,755	$ 276	$ 195,452	$ 452,877	$ 617	$ (29,467)