Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Amortized cost	$ 1,871,260,000	$ 2,094,826,000
Allowance for credit losses for available-for-sale securities	$ 0	$ 0
Common Stock, stated value (in dollars per share)	$ 1	$ 1
Common Stock, shares authorized (in shares)	45,000,000	45,000,000