Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Surplus	Accumulated Other Comprehensive Income (Loss)	Undivided Profits
Beginning 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 (loss)	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)
Ending balance at Mar. 31, 2023	3,339,901	1,273	2,533,589	(470,681)	1,275,720
Beginning balance at Dec. 31, 2023	3,426,488	1,252	2,499,930	(404,375)	1,329,681
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	35,230			(3,641)	38,871
Stock issued for employee stock purchase plan	970		970
Stock-based compensation plans, net	2,775	2	2,773
Dividends on common stock	(26,337)				(26,337)
Ending balance at Mar. 31, 2024	$ 3,439,126	$ 1,254	$ 2,503,673	$ (408,016)	$ 1,342,215