Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at Dec. 31, 2023	$ 3,803,661	$ 309,513	$ 1,739,671	$ 2,375,604	$ (621,127)
Balance, Shares Issued at Dec. 31, 2023		92,947
Net income	223,169			223,169
Other comprehensive income (loss)	(36,809)				(36,809)
Comprehensive income	186,360
Cash dividends declared	(61,801)			(61,801)
Common stock activity, long-term incentive plans	5,102		5,017	85
Issuance of stock from dividend reinvestment and stock purchase plans	2,018		2,018
Repurchase of common stock	(14,622)		(14,622)
Balance at Jun. 30, 2024	3,920,718	$ 309,513	1,732,084	2,537,057	(657,936)
Balance, Shares Issued at Jun. 30, 2024		92,947
Balance at Mar. 31, 2024	3,853,436	$ 309,513	1,739,702	2,457,736	(653,515)
Balance, Shares Issued at Mar. 31, 2024		92,947
Net income	114,557			114,557
Other comprehensive income (loss)	(4,421)				(4,421)
Comprehensive income	110,136
Cash dividends declared	(35,274)			(35,274)
Common stock activity, long-term incentive plans	5,921		5,883	38
Issuance of stock from dividend reinvestment and stock purchase plans	1,121		1,121
Repurchase of common stock	(14,622)		(14,622)
Balance at Jun. 30, 2024	3,920,718	$ 309,513	1,732,084	2,537,057	(657,936)
Balance, Shares Issued at Jun. 30, 2024		92,947
Balance at Dec. 31, 2024	$ 4,127,636	$ 309,513	1,719,609	2,704,606	(606,092)
Balance, Shares Issued at Dec. 31, 2024	92,947	92,947
Net income	$ 233,035			233,035
Other comprehensive income (loss)	136,265				136,265
Comprehensive income	369,300
Cash dividends declared	(78,614)			(78,614)
Common stock activity, long-term incentive plans	5,349		5,338	11
Issuance of stock from dividend reinvestment and stock purchase plans	2,212		2,212
Repurchase of common stock	(60,464)		(60,464)
Balance at Jun. 30, 2025	$ 4,365,419	$ 309,513	1,666,695	2,859,038	(469,827)
Balance, Shares Issued at Jun. 30, 2025	92,947	92,947
Balance at Mar. 31, 2025	$ 4,278,672	$ 309,513	1,699,474	2,784,657	(514,972)
Balance, Shares Issued at Mar. 31, 2025		92,947
Net income	113,531			113,531
Other comprehensive income (loss)	45,145				45,145
Comprehensive income	158,676
Cash dividends declared	(39,154)			(39,154)
Common stock activity, long-term incentive plans	5,813		5,809	4
Issuance of stock from dividend reinvestment and stock purchase plans	1,129		1,129
Repurchase of common stock	(39,717)		(39,717)
Balance at Jun. 30, 2025	$ 4,365,419	$ 309,513	$ 1,666,695	$ 2,859,038	$ (469,827)
Balance, Shares Issued at Jun. 30, 2025	92,947	92,947