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 Income (Loss) [Member]
Balance at Dec. 31, 2021	$ 3,670,352	$ 309,513	$ 1,755,701	$ 1,659,073	$ (53,935)
Balance, Shares Issued at Dec. 31, 2021		92,947
Net income	123,478			123,478
Other comprehensive income (loss)	(305,341)				(305,341)
Comprehensive income (loss)	(181,863)			123,478	(305,341)
Cash dividends declared	(23,909)			(23,909)
Common stock activity, long-term incentive plans	3,980		3,929	51
Repurchase of common stock	(18,490)		(18,490)
Issuance of stock from dividend reinvestment and stock purchase plans	881		881
Balance at Mar. 31, 2022	3,450,951	$ 309,513	1,742,021	1,758,693	(359,276)
Balance, Shares Issued at Mar. 31, 2022		92,947
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	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
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	92,947