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, 2019		28,386,456
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	$ 1,003,477	$ 301	$ 332,861	$ 708,579	$ (38,264)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	239,874			239,874
Treasury Stock, Shares, Acquired		(80,000)
Treasury Stock, Value, Acquired, Cost Method	(1,912)				(1,912)
Stock options exercised - shares		422,820
Stock options exercised - value	9,906		636		9,270
Stock-based compensation expense	7,138		7,138
Deferral of Executive and Director Compensation	215		215
Deferred Compensation Arrangement with Individual, Shares Issued		84,573
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(1,849)		1,849
Shares Outstanding, Ending Balance at Dec. 31, 2020		28,813,849
Stockholders' Equity, Ending Balance at Dec. 31, 2020	1,258,698	$ 301	339,001	948,453	(29,057)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 396,868			396,868
Treasury Stock, Shares, Acquired	800,000	(842,500)
Treasury Stock, Value, Acquired, Cost Method	$ (51,520)				(51,520)
Stock options exercised - shares		452,100
Stock options exercised - value	11,241		1,227		10,014
Stock-based compensation expense	8,559		8,559
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 Dec. 31, 2021		28,499,630
Stockholders' Equity, Ending 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	$ 490,662			490,662
Treasury Stock, Shares, Acquired	1,200,000	(1,200,000)
Treasury Stock, Value, Acquired, Cost Method	$ (55,334)				(55,334)
Stock options exercised - shares	49,900	49,900
Stock options exercised - value	$ 1,366		(810)		2,176
Stock-based compensation expense	8,787		8,787
Deferral of Executive and Director Compensation	1,060		1,060
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 Dec. 31, 2022		27,440,083
Stockholders' Equity, Ending Balance at Dec. 31, 2022	$ 2,070,725	$ 301	$ 352,639	$ 1,835,983	$ (118,198)