Consolidated Statements Of Shareholders' Equity - USD ($) $ in Thousands	Total	Common stock	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning of year at Dec. 31, 2018		$ 98,026	$ 1,519,658	$ 0	$ 1,519,658
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds of stock options exercised		701
Share-based compensation expense		123
Withholding tax on stock options exercised		(22)
Net income	$ 320,087		320,087
Dividends paid to shareholders			(139,071)
End of year at Dec. 31, 2019	1,799,502	98,828	1,700,674	(2,014)	1,698,660
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds of stock options exercised		0
Share-based compensation expense		142
Withholding tax on stock options exercised		0
Net income	374,607		374,607
Dividends paid to shareholders			(139,640)
End of year at Dec. 31, 2020	2,032,597	98,970	1,933,627	$ 0	$ 1,933,627
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds of stock options exercised		215
Share-based compensation expense		141
Withholding tax on stock options exercised		(383)
Net income	247,937		247,937
Dividends paid to shareholders			(140,226)
End of year at Dec. 31, 2021	$ 2,140,281	$ 98,943	$ 2,041,338