Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Capital Stock, Common	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2018	$ 615,972	$ 907	$ 3,454	$ 760,262	$ (148,651)
Net income	17,318	0	0	17,318	0
Dividends on common stock, $0.02 per share	(1,640)	0	0	(1,640)	0
Stock-based compensation, net of tax	177	0	(30)	0	207
Balance at Mar. 31, 2019	631,827	907	3,424	775,940	(148,444)
Net income	22,361	0	0	22,361	0
Dividends on common stock, $0.02 per share	(1,640)	0	0	(1,640)	0
Stock-based compensation, net of tax	781	0	375	0	406
Balance at Jun. 30, 2019	653,329	907	3,799	796,661	(148,038)
Net income	20,501	0	0	20,501	0
Dividends on common stock, $0.02 per share	(1,642)	0	0	(1,642)	0
Stock-based compensation, net of tax	197	0	33	0	164
Proceeds from Issuance of Common Stock	750	0	113	0	637
Balance at Sep. 30, 2019	673,135	907	3,945	815,520	(147,237)
Balance at Dec. 31, 2019	684,659	907	4,141	826,666	(147,055)
Net income	13,238	0	0	13,238	0
Dividends on common stock, $0.02 per share	(1,628)	0	0	(1,628)	0
Repurchases of common stock	(12,278)	0	0	0	(12,278)
Stock-based compensation, net of tax	697	0	291	0	406
Balance at Mar. 31, 2020	684,688	907	4,432	838,276	(158,927)
Net income	19,182	0	0	19,182	0
Dividends on common stock, $0.02 per share	(1,628)	0	0	(1,628)	0
Stock-based compensation, net of tax	373	0	174	0	199
Balance at Jun. 30, 2020	702,615	907	4,606	855,830	(158,728)
Net income	20,714	0	0	20,714	0
Dividends on common stock, $0.02 per share	(1,628)	0	0	(1,628)	0
Stock-based compensation, net of tax	8	0	(208)	0	216
Balance at Sep. 30, 2020	$ 721,709	$ 907	$ 4,398	$ 874,916	$ (158,512)