Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Surplus	Accumulated Other Comprehensive (Loss) Income	Undivided Profits
Balance at Dec. 31, 2021	$ 3,248,841	$ 1,127	$ 2,164,989	$ (10,545)	$ 1,093,270
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	(251,321)			(316,416)	65,095
Stock issued for employee stock purchase plan	1,151	1	1,150
Stock-based compensation plans, net	366	2	364
Stock repurchases	(16,055)	(5)	(16,050)
Dividends on common stock	(21,375)				(21,375)
Balance at Mar. 31, 2022	2,961,607	1,125	2,150,453	(326,961)	1,136,990
Balance at Dec. 31, 2022	3,269,362	1,270	2,530,066	(517,560)	1,255,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	92,468			46,879	45,589
Stock issued for employee stock purchase plan	833		833
Stock-based compensation plans, net	2,693	3	2,690
Dividends on common stock	(25,455)				(25,455)
Balance at Mar. 31, 2023	$ 3,339,901	$ 1,273	$ 2,533,589	$ (470,681)	$ 1,275,720