Condensed Consolidated Statement Of Stockholders' Equity - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock
Beginning balance at Dec. 31, 2017	$ 652,745	$ 277	$ 203,990	$ 475,506	$ 2,439	$ (29,467)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,336			47,336
Issuance of 223,768 shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(14,085)	2	(14,087)
Stock-based compensation expense	5,543		5,543
Other comprehensive income					1,110
Cash dividends ($0.55 per share)	(13,858)			(13,858)
Dividend equivalents on stock-based awards			319	(319)
Ending balance at Mar. 31, 2018	$ 678,791	$ 279	$ 195,765	$ 508,665	$ 3,549	$ (29,467)