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)	151,475			47,572	103,903
Stock issued for employee stock purchase plan	833		833
Stock-based compensation plans, net	5,513	3	5,510
Stock repurchases	(20,022)	(11)	(20,011)
Dividends on common stock	(50,835)				(50,835)
Ending balance at Jun. 30, 2023	3,356,326	1,262	2,516,398	(469,988)	1,308,654
Beginning balance at Mar. 31, 2023	3,339,901	1,273	2,533,589	(470,681)	1,275,720
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	59,007			693	58,314
Stock-based compensation plans, net	2,820	0	2,820
Stock repurchases	(20,022)	(11)	(20,011)
Dividends on common stock	(25,380)				(25,380)
Ending balance at Jun. 30, 2023	3,356,326	1,262	2,516,398	(469,988)	1,308,654
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)	78,528			(1,106)	79,634
Stock issued for employee stock purchase plan	970		970
Stock-based compensation plans, net	5,572	3	5,569
Dividends on common stock	(52,689)				(52,689)
Ending balance at Jun. 30, 2024	3,458,869	1,255	2,506,469	(405,481)	1,356,626
Beginning balance at Mar. 31, 2024	3,439,126	1,254	2,503,673	(408,016)	1,342,215
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	43,298			2,535	40,763
Stock-based compensation plans, net	2,797	1	2,796
Dividends on common stock	(26,352)				(26,352)
Ending balance at Jun. 30, 2024	$ 3,458,869	$ 1,255	$ 2,506,469	$ (405,481)	$ 1,356,626