Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,479,545,000	$ 1,673,864,000
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0	$ 0
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, par value	$ 25	$ 25
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	19,047,548	19,047,548
Common stock, treasury shares	4,215,731	4,259,399