Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Capital Stock, Common	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2019	$ 684,659	$ 907	$ 4,141	$ 826,666	$ (147,055)
Net income	13,238	0	0	13,238	0
Dividends, Common Stock	(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, Common Stock	(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, Common Stock	(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)
Balance at Dec. 31, 2020	724,334	907	4,330	890,970	(171,873)
Net income	13,734	0	0	13,734	0
Dividends, Common Stock	(1,599)	0	0	(1,599)	0
Repurchases of common stock	(14,537)	0	0	0	(14,537)
Stock-based compensation, net of tax	485	0	146	0	339
Balance at Mar. 31, 2021	722,417	907	4,476	903,105	(186,071)
Net income	20,742	0	0	20,742	0
Dividends, Common Stock	(1,598)	0	0	(1,598)	0
Stock-based compensation, net of tax	205	0	55	0	150
Balance at Jun. 30, 2021	741,766	907	4,531	922,249	(185,921)
Net income	24,466	0	0	24,466	0
Dividends, Common Stock	(41,095)	0	0	(41,095)	0
Repurchases of common stock	(16,400)	0	0	0	(16,400)
Stock-based compensation, net of tax	79	0	(212)	0	291
Balance at Sep. 30, 2021	$ 708,816	$ 907	$ 4,319	$ 905,620	$ (202,030)