Derivatives (Credit Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2025	Jun. 30, 2024	Dec. 31, 2024
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 201		$ 196
Maximum Amount of Future Payments under Credit Default Swaps	$ 12,096		11,764
Weighted Average Years to Maturity	4 years	3 years 4 months 24 days
Aaa/Aa/A
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 66		73
Maximum Amount of Future Payments under Credit Default Swaps	$ 4,222		4,198
Weighted Average Years to Maturity	2 years	2 years 2 months 12 days
Aaa/Aa/A | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1		1
Maximum Amount of Future Payments under Credit Default Swaps	$ 96		72
Weighted Average Years to Maturity	1 year 8 months 12 days	1 year 10 months 24 days
Aaa/Aa/A | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 65		72
Maximum Amount of Future Payments under Credit Default Swaps	$ 4,126		4,126
Weighted Average Years to Maturity	2 years	2 years 2 months 12 days
Baa
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 119		112
Maximum Amount of Future Payments under Credit Default Swaps	$ 7,507		7,365
Weighted Average Years to Maturity	5 years 2 months 12 days	4 years 1 month 6 days
Baa | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1		1
Maximum Amount of Future Payments under Credit Default Swaps	$ 71		102
Weighted Average Years to Maturity	1 year 2 months 12 days	1 year 7 months 6 days
Baa | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 118		111
Maximum Amount of Future Payments under Credit Default Swaps	$ 7,436		7,263
Weighted Average Years to Maturity	5 years 2 months 12 days	4 years 1 month 6 days
B
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 16		10
Maximum Amount of Future Payments under Credit Default Swaps	$ 327		144
Weighted Average Years to Maturity	4 years 1 month 6 days	3 years 8 months 12 days
B | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 0		0
Maximum Amount of Future Payments under Credit Default Swaps	$ 23		0
Weighted Average Years to Maturity	1 year	0 years
B | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 16		10
Maximum Amount of Future Payments under Credit Default Swaps	$ 304		144
Weighted Average Years to Maturity	4 years 4 months 24 days	3 years 8 months 12 days
Caa
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ (1)		(1)
Maximum Amount of Future Payments under Credit Default Swaps	$ 15		15
Weighted Average Years to Maturity	1 year 8 months 12 days	2 years
Caa | 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	$ 15		15
Weighted Average Years to Maturity	1 year 8 months 12 days	2 years
Ba
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1		2
Maximum Amount of Future Payments under Credit Default Swaps	$ 25		42
Weighted Average Years to Maturity	1 year 8 months 12 days	1 year 7 months 6 days
Ba | Single name credit default swaps (3)
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 0		0
Maximum Amount of Future Payments under Credit Default Swaps	$ 0		17
Weighted Average Years to Maturity	0 years	1 year 1 month 6 days
Ba | Credit default swaps referencing indices
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 1		2
Maximum Amount of Future Payments under Credit Default Swaps	$ 25		$ 25
Weighted Average Years to Maturity	1 year 8 months 12 days	2 years