Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation Trust [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2018	$ 695,864	$ 26	$ 254,738	$ (3,381)	$ 444,481
Beginning Balance, Shares at Dec. 31, 2018		25,693,651
Stock compensation, including options and long-term incentives	4,977		4,977
Director deferred share activity	1,210		1,210
Director deferred share activity , Shares		49,750
Exercise of stock options less shares withheld for taxes	2,927		2,927
Exercise of stock options less shares withheld for taxes, Shares		107,171
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		85,960
Shares issued for long-term incentive awards, net of shares withheld for taxes	(3,471)		(3,471)
Purchase of shares by Deferred Compensation Trust	(83)		687	(770)
Sale of shares by Deferred Compensation Trust	83		(197)	280
Net income	113,719				113,719
Ending Balance at Dec. 31, 2019	815,226	$ 26	260,871	(3,871)	558,200
Ending Balance, Shares at Dec. 31, 2019		25,936,532
Stock compensation, including options and long-term incentives	6,306		6,306
Director deferred share activity	1,230		1,230
Director deferred share activity , Shares		132,421
Exercise of stock options less shares withheld for taxes	3,786		3,786
Exercise of stock options less shares withheld for taxes, Shares		108,240
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		59,377
Shares issued for long-term incentive awards, net of shares withheld for taxes	(3,600)		(3,600)
Purchase of shares by Deferred Compensation Trust			1,275	(1,275)
Sale of shares by Deferred Compensation Trust			(2,202)	2,202
Net income	138,340				138,340
Ending Balance at Dec. 31, 2020	961,288	$ 26	267,666	(2,944)	696,540
Ending Balance, Shares at Dec. 31, 2020		26,236,570
Stock compensation, including options and long-term incentives	7,245		7,245
Director deferred share activity	1,458		1,458
Director deferred share activity , Shares		1,698
Exercise of stock options less shares withheld for taxes	$ 3,678		3,678
Exercise of stock options less shares withheld for taxes, Shares	46,741	46,741
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		51,580
Shares issued for long-term incentive awards, net of shares withheld for taxes	$ (6,571)		(6,571)
Purchase of shares by Deferred Compensation Trust			1,268	(1,268)
Sale of shares by Deferred Compensation Trust			(111)	111
Net income	253,235				253,235
Ending Balance at Dec. 31, 2021	$ 1,220,333	$ 26	$ 274,633	$ (4,101)	$ 949,775
Ending Balance, Shares at Dec. 31, 2021		26,336,589