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, 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	360,083			360,083
Stock options exercised, shares		778,358
Stock options exercised	27,152		(7,858)		35,010
Stock-based compensation expense	7,006		7,006
Repurchase of common shares, shares		(473,000)
Repurchase of common shares	(40,259)				(40,259)
Deferral of executive and director compensation	1,005		1,005
Deferred Compensation Arrangement with Individual, Shares Issued		103,081
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(4,630)		4,630
Shares Outstanding, Ending Balance at Sep. 30, 2023		27,848,522
Stockholders' Equity, Ending Balance at Sep. 30, 2023	2,425,712	$ 301	348,162	2,196,066	(118,817)
Shares Outstanding, Beginning Balance at Jun. 30, 2023		27,782,616
Stockholders' Equity, Beginning Balance at Jun. 30, 2023	2,298,459		350,127	2,057,050	(109,019)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	139,016			139,016
Stock options exercised, shares		283,292
Stock options exercised	10,583		(2,559)		13,142
Stock-based compensation expense	2,682		2,682
Repurchase of common shares, shares		(263,000)
Repurchase of common shares	(25,052)				(25,052)
Deferral of executive and director compensation	24		24
Deferred Compensation Arrangement with Individual, Shares Issued		45,614
Deferred Compensation Arrangement with Individual, Distribution Paid			(2,112)		2,112
Shares Outstanding, Ending Balance at Sep. 30, 2023		27,848,522
Stockholders' Equity, Ending Balance at Sep. 30, 2023	2,425,712	$ 301	348,162	2,196,066	(118,817)
Shares Outstanding, Beginning Balance at Dec. 31, 2023		27,761,299
Stockholders' Equity, Beginning Balance at Dec. 31, 2023	2,516,939	$ 301	349,907	2,301,348	(134,617)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	430,256			430,256
Stock options exercised, shares		310,696
Stock options exercised	13,034		(7,172)		20,206
Stock-based compensation expense	10,859		10,859
Repurchase of common shares, shares		(922,000)
Repurchase of common shares	(125,819)				(125,819)
Deferral of executive and director compensation	87		87
Deferred Compensation Arrangement with Individual, Shares Issued		55,059
Deferred Compensation Arrangement with Individual, Distribution Paid	0		(3,137)		3,137
Shares Outstanding, Ending Balance at Sep. 30, 2024		27,205,054
Stockholders' Equity, Ending Balance at Sep. 30, 2024	2,845,356	$ 301	350,544	2,731,604	(237,093)
Shares Outstanding, Beginning Balance at Jun. 30, 2024		27,403,908
Stockholders' Equity, Beginning Balance at Jun. 30, 2024	2,741,117	$ 301	350,554	2,586,155	(195,893)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	145,449			145,449
Stock options exercised, shares		123,146
Stock options exercised	5,485		(3,549)		9,034
Stock-based compensation expense	$ 3,510		3,510
Repurchase of common shares, shares	300,000	(322,000)
Repurchase of common shares	$ (50,234)				(50,234)
Deferral of executive and director compensation	29		29
Deferred Compensation Arrangement with Individual, Shares Issued		0
Deferred Compensation Arrangement with Individual, Distribution Paid	0		0		0
Shares Outstanding, Ending Balance at Sep. 30, 2024		27,205,054
Stockholders' Equity, Ending Balance at Sep. 30, 2024	$ 2,845,356	$ 301	$ 350,544	$ 2,731,604	$ (237,093)