Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Statement Of Financial Position [Abstract]
Available for sale securities, amortized cost	$ 7,992,603	$ 11,822,584
Held to maturity securities, allowance for credit losses	2,519	1,940
Held to Maturity, Fair value	$ 5,079,806	$ 1,442,391
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares authorized	80,000,000	80,000,000
Common stock, shares issued	55,056,730	55,056,730
Common stock, shares outstanding	48,309,638	48,430,805
Treasury stock, shares	6,747,092	6,625,925