Derivatives (Credit Derivatives) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 20	$ 16
Maximum Amount of Future Payments under Credit Default Swaps	$ 1,530	$ 1,757
Weighted Average Years to Maturity (2)	3 years 9 months 18 days	4 years 1 month 6 days
Credit default swaps | Aaa/Aa/A
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 7	$ 7
Maximum Amount of Future Payments under Credit Default Swaps	$ 544	$ 544
Weighted Average Years to Maturity (2)	1 year 6 months	2 years 2 months 12 days
Credit default swaps | Baa
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 12	$ 8
Maximum Amount of Future Payments under Credit Default Swaps	$ 958	$ 1,185
Weighted Average Years to Maturity (2)	5 years 2 months 12 days	5 years
Credit default swaps | Ba
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 2	$ 2
Maximum Amount of Future Payments under Credit Default Swaps	$ 24	$ 24
Weighted Average Years to Maturity (2)	3 years 2 months 12 days	4 years
Credit default swaps | Caa and Lower
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ (1)	$ (1)
Maximum Amount of Future Payments under Credit Default Swaps	$ 4	$ 4
Weighted Average Years to Maturity (2)	2 years 2 months 12 days	3 years