Derivatives (Credit Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 129	$ 165
Maximum Amount of Future Payments under Credit Default Swaps	$ 10,518	$ 8,626
Weighted Average Years to Maturity	5 years 1 month 6 days	4 years 7 months 6 days
Aaa/Aa/A
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 25	$ 21
Maximum Amount of Future Payments under Credit Default Swaps	$ 2,077	$ 1,350
Weighted Average Years to Maturity	3 years 2 months 12 days	2 years 7 months 6 days
Aaa/Aa/A | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 3	$ 4
Maximum Amount of Future Payments under Credit Default Swaps	$ 159	$ 159
Weighted Average Years to Maturity	2 years 10 months 24 days	3 years 1 month 6 days
Aaa/Aa/A | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 22	$ 17
Maximum Amount of Future Payments under Credit Default Swaps	$ 1,918	$ 1,191
Weighted Average Years to Maturity	3 years 2 months 12 days	2 years 6 months
Baa [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 109	$ 148
Maximum Amount of Future Payments under Credit Default Swaps	$ 8,294	$ 7,089
Weighted Average Years to Maturity	5 years 7 months 6 days	5 years
Baa [Member] | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 2	$ 2
Maximum Amount of Future Payments under Credit Default Swaps	$ 146	$ 101
Weighted Average Years to Maturity	1 year 10 months 24 days	3 years 4 months 24 days
Baa [Member] | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 107	$ 146
Maximum Amount of Future Payments under Credit Default Swaps	$ 8,148	$ 6,988
Weighted Average Years to Maturity	5 years 8 months 12 days	5 years
B
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 3	$ 5
Maximum Amount of Future Payments under Credit Default Swaps	$ 55	$ 55
Weighted Average Years to Maturity	3 years 8 months 12 days	4 years
B | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 3	$ 5
Maximum Amount of Future Payments under Credit Default Swaps	$ 55	$ 55
Weighted Average Years to Maturity	3 years 8 months 12 days	4 years
Ba
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1	$ 0
Maximum Amount of Future Payments under Credit Default Swaps	$ 62	$ 102
Weighted Average Years to Maturity	4 years 6 months	2 years
Ba | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 0	$ 1
Maximum Amount of Future Payments under Credit Default Swaps	$ 17	$ 82
Weighted Average Years to Maturity	3 years 10 months 24 days	1 year 2 months 12 days
Ba | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1	$ (1)
Maximum Amount of Future Payments under Credit Default Swaps	$ 45	$ 20
Weighted Average Years to Maturity	4 years 8 months 12 days	5 years
Caa3
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ (9)	$ (9)
Maximum Amount of Future Payments under Credit Default Swaps	$ 30	$ 30
Weighted Average Years to Maturity	4 years 2 months 12 days	4 years 6 months
Caa3 | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ (9)	$ (9)
Maximum Amount of Future Payments under Credit Default Swaps	$ 30	$ 30
Weighted Average Years to Maturity	4 years 2 months 12 days	4 years 6 months