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, 2022	$ 3,342,628	$ 309,513	$ 1,716,884	$ 2,088,413	$ (772,182)
Balance, Shares Issued at Dec. 31, 2022		92,947
Net income	126,467			126,467
Other comprehensive income (loss)	84,717				84,717
Comprehensive income (loss)	211,184			126,467	84,717
Cash dividends declared	(26,387)			(26,387)
Common stock activity, long-term incentive plans	2,872		2,804	68
Issuance of stock from dividend reinvestment and stock purchase plans	935		935
Balance at Mar. 31, 2023	3,531,232	$ 309,513	1,720,623	2,188,561	(687,465)
Balance, Shares Issued at Mar. 31, 2023		92,947
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	92,947
Net income	$ 108,612			108,612
Other comprehensive income (loss)	(32,388)				(32,388)
Comprehensive income (loss)	76,224			108,612	(32,388)
Cash dividends declared	(26,527)			(26,527)
Common stock activity, long-term incentive plans	(819)		(866)	47
Issuance of stock from dividend reinvestment and stock purchase plans	897		897
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	92,947