Condensed Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Shares [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock, Common
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		(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)
Shares Outstanding, Beginning Balance at Dec. 31, 2022		27,440,083
Stockholders' Equity, Beginning Balance at Dec. 31, 2022	2,070,725	$ 301	352,639	1,835,983	(118,198)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	103,066			103,066
Stock options exercised, shares		218,066
Stock options exercised	6,439		(3,118)		9,557
Stock-based compensation expense	$ 2,023		2,023
Repurchase of common shares, shares	0
Deferral of executive and director compensation	$ 962		962
Deferred Compensation Arrangement with Individual, Shares Issued		57,467
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(2,518)		2,518
Shares Outstanding, Ending Balance at Mar. 31, 2023		27,715,616
Stockholders' Equity, Ending Balance at Mar. 31, 2023	$ 2,183,215	$ 301	$ 349,988	$ 1,939,049	$ (106,123)