Condensed Consolidated Statement Of Stockholders' Equity - 6 months ended Jun. 30, 2016 - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance - December 31, 2015 at Dec. 31, 2015	$ 438,575	$ 270	$ 166,566	$ 301,206	$ 0	$ (29,467)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,528			73,528
Issuance of 231,979 shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(3,803)	3	(3,806)
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	2,659		2,659
Stock-based compensation expense	7,274		7,274
Issuance of 4,784 deferred stock units relating to prior year compensation	264		264
Other comprehensive loss	(759)				(759)
Cash dividends ($0.60 per share)	(14,707)			(14,707)
Dividend equivalents on stock-based awards			517	(517)
Balance - March 31, 2016 at Jun. 30, 2016	$ 503,031	$ 273	$ 173,474	$ 359,510	$ (759)	$ (29,467)