Condensed Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Shares [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Shares [Member]
Shares Outstanding, Beginning Balance at Dec. 31, 2020		28,813,849
Stockholders' Equity, Beginning Balance at Dec. 31, 2020	$ 1,258,698	$ 301	$ 339,001	$ 948,453	$ (29,057)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	84,866			84,866
Stock options exercised, shares		295,600
Stock options exercised	7,256		766		6,490
Stock-based compensation expense	2,264		2,264
Deferral of executive and director compensation	338		338
Deferred Compensation Arrangement with Individual, Shares Issued		76,181
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(1,673)		1,673
Shares Outstanding, Ending Balance at Mar. 31, 2021		29,185,630
Stockholders' Equity, Ending Balance at Mar. 31, 2021	1,353,422	$ 301	340,696	1,033,319	(20,894)
Shares Outstanding, Beginning Balance at Dec. 31, 2021		28,499,630
Stockholders' Equity, Beginning Balance at Dec. 31, 2021	1,624,184	$ 301	347,452	1,345,321	(68,890)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	91,839			91,839
Stock options exercised, shares		8,600
Stock options exercised	206		(164)		370
Stock-based compensation expense	$ 1,831		1,831
Repurchase of common shares, shares	300,000	(310,000)
Repurchase of common shares	$ (15,393)				(15,393)
Deferral of executive and director compensation	1,022		1,022
Deferred Compensation Arrangement with Individual, Shares Issued		90,553
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(3,850)		3,850
Shares Outstanding, Ending Balance at Mar. 31, 2022		28,288,783
Stockholders' Equity, Ending Balance at Mar. 31, 2022	$ 1,703,689	$ 301	$ 346,291	$ 1,437,160	$ (80,063)