Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investments, Unrealized Loss Position
Gross unrealized loss	$ 1,236	$ 908
Corporate
Investments, Unrealized Loss Position
Gross unrealized loss	700	580
States, municipalities and political subdivisions
Investments, Unrealized Loss Position
Gross unrealized loss	489	303
Government-sponsored enterprises
Investments, Unrealized Loss Position
Gross unrealized loss	23	3
United States government
Investments, Unrealized Loss Position
Gross unrealized loss	6	5
Commercial mortgage-backed
Investments, Unrealized Loss Position
Gross unrealized loss	18	16
Foreign government
Investments, Unrealized Loss Position
Gross unrealized loss	0	1
Fixed maturities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	4,446	8,760
Less than 12 Months, Unrealized Loss	165	706
12 months or more, Fair Value	7,757	800
12 months or longer, Unrealized Loss	1,071	202
Total Fair Value	12,203	9,560
Gross unrealized loss	1,236	908
Fixed maturities | Corporate
Investments, Unrealized Loss Position
Less than 12 months Fair Value	1,283	5,651
Less than 12 Months, Unrealized Loss	58	412
12 months or more, Fair Value	5,431	661
12 months or longer, Unrealized Loss	642	168
Total Fair Value	6,714	6,312
Gross unrealized loss	700	580
Fixed maturities | States, municipalities and political subdivisions
Investments, Unrealized Loss Position
Less than 12 months Fair Value	2,331	2,600
Less than 12 Months, Unrealized Loss	89	274
12 months or more, Fair Value	1,902	77
12 months or longer, Unrealized Loss	400	29
Total Fair Value	4,233	2,677
Gross unrealized loss	489	303
Fixed maturities | Government-sponsored enterprises
Investments, Unrealized Loss Position
Less than 12 months Fair Value	742	123
Less than 12 Months, Unrealized Loss	17	3
12 months or more, Fair Value	95	3
12 months or longer, Unrealized Loss	6	0
Total Fair Value	837	126
Gross unrealized loss	23	3
Fixed maturities | United States government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	80	146
Less than 12 Months, Unrealized Loss	1	3
12 months or more, Fair Value	130	41
12 months or longer, Unrealized Loss	5	2
Total Fair Value	210	187
Gross unrealized loss	6	5
Fixed maturities | Commercial mortgage-backed
Investments, Unrealized Loss Position
Less than 12 months Fair Value	1	215
Less than 12 Months, Unrealized Loss	0	13
12 months or more, Fair Value	194	14
12 months or longer, Unrealized Loss	18	3
Total Fair Value	195	229
Gross unrealized loss	18	16
Fixed maturities | Foreign government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	9	25
Less than 12 Months, Unrealized Loss	0	1
12 months or more, Fair Value	5	4
12 months or longer, Unrealized Loss	0	0
Total Fair Value	14	29
Gross unrealized loss	$ 0	$ 1