Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Capital Stock, Common	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2016	$ 505,826	$ 907	$ 3,433	$ 625,668	$ (124,182)
Net income	75,173	0	0	75,173	0
Dividends on common stock	(6,667)	0	0	(6,667)	0
Stock-based compensation, net of tax	313	0	85	0	228
Balance at Dec. 31, 2017	574,645	907	3,518	694,174	(123,954)
Net income	72,677	0	0	72,677	0
Dividends on common stock	(6,589)	0	0	(6,589)	0
Stock-based compensation, net of tax	326	0	(64)	0	390
Stock Repurchased During Period, Value	(25,087)	0	0	0	(25,087)
Balance at Dec. 31, 2018	615,972	907	3,454	760,262	(148,651)
Net income	72,967	0	0	72,967	0
Dividends on common stock	(6,563)	0	0	(6,563)	0
Stock-based compensation, net of tax	1,533	0	574	0	959
Stock Issued During Period, Value	750	0	113	0	637
Balance at Dec. 31, 2019	$ 684,659	$ 907	$ 4,141	$ 826,666	$ (147,055)