Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Amortized cost	$ 1,796,040,000	$ 1,871,260,000
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