Investments (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Equity Securities, FV-NI	$ 7,500,000	$ 7,600,000
Federal Home Loan Bank Stock and Federal Reserve Bank Stock	23,500,000	15,500,000
Certificates of Deposit, at Carrying Value		700,000
nongovernmentalissuerover10%ofequity	0	0
Credit-related net investment impairment losses	0	0	$ 0
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	0
Asset Pledged as Collateral
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 709,000,000	$ 886,000,000