CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2018	$ 288	$ 115,842	$ 441,010	$ (31,237)	$ 525,903
Balance (in shares) at Dec. 31, 2018	28,787			(2,391)
Stock-based compensation expense		269			269
Restricted stock units vested (in shares)	3
Issuance of common stock under Employee Stock Purchase Plan		(13)			(13)
Repurchase of common stock for treasury				$ (1,294)	(1,294)
Repurchase of common stock for treasury (in shares)				(43)
Net income			12,727		12,727
Balance at Mar. 31, 2019	$ 288	116,098	453,737	$ (32,531)	537,592
Balance (in shares) at Mar. 31, 2019	28,790			(2,434)
Balance at Dec. 31, 2019	$ 288	118,045	514,694	$ (35,715)	597,312
Balance (in shares) at Dec. 31, 2019	28,870			(2,526)
Stock-based compensation expense		624			624
Restricted stock units vested	$ 1				1
Restricted stock units vested (in shares)	4
Shares withheld for taxes paid on stock awards		(49)			(49)
Repurchase of common stock for treasury				$ (10,222)	(10,222)
Repurchase of common stock for treasury (in shares)				(247)
Net income			14,896		14,896
Balance at Mar. 31, 2020	$ 289	$ 118,620	$ 529,590	$ (45,937)	$ 602,562
Balance (in shares) at Mar. 31, 2020	28,874			(2,773)