Condensed Consolidated Statement Of Stockholders' Equity - 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 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 (loss)					1,110
Cash dividends	(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)
Beginning balance at Dec. 31, 2018	706,255	280	203,246	563,496	(2,605)	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,366			34,366
Issuance of shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(6,348)	1	(6,349)
Stock-based compensation expense	3,733		3,733
Other comprehensive income (loss)					(1,328)
Cash dividends	(14,999)			(14,999)
Dividend equivalents on stock-based awards			304	(304)
Ending balance at Mar. 31, 2019	$ 721,679	$ 281	$ 200,934	$ 582,559	$ (3,933)	$ (58,162)