Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Interest bearing deposits, banks	$ 342,070,000	$ 242,229,000
Held-to-maturity securities, fair values	$ 998,987,000	$ 1,084,390,000
Preferred stock, no par value
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	150,000	150,000
Preferred stock, shares outstanding	150,000	150,000
6.75% non-cumulative perpetual preferred stock, Series A, liquidation preference	$ 150,000,000	$ 150,000,000
Common stock, par value	$ 2.0833	$ 2.0833
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	68,081,306	68,081,306
Common stock, shares outstanding	59,364,696	59,198,963
Treasury stock, shares	8,716,610	8,882,343