Investments - Available for Sale Securities in Continuous Unrealized Loss Position (Details) $ in Millions	Sep. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 19,962	$ 11,248
Fair Value, 12 Months or More	12,586	31,037
Fair Value, Total	32,548	42,285
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	193	493
Gross Unrealized Losses, 12 Months or More	2,574	3,392
Gross Unrealized Losses, Total	$ 2,767	$ 3,885
Number of securities in an unrealized loss position | security	10,479	13,052
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	8,111	10,027
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 533	$ 1,027
Fair Value, 12 Months or More	502	804
Fair Value, Total	1,035	1,831
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	2	10
Gross Unrealized Losses, 12 Months or More	67	79
Gross Unrealized Losses, Total	69	89
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	1,779	850
Fair Value, 12 Months or More	25	1,602
Fair Value, Total	1,804	2,452
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	15	24
Gross Unrealized Losses, 12 Months or More	82	133
Gross Unrealized Losses, Total	97	157
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	1,286	1,431
Fair Value, 12 Months or More	3,896	4,503
Fair Value, Total	5,182	5,934
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	34	87
Gross Unrealized Losses, 12 Months or More	507	583
Gross Unrealized Losses, Total	541	670
Corporate debt
Fair Value
Fair Value, Less than 12 Months	10,953	4,089
Fair Value, 12 Months or More	7,554	18,612
Fair Value, Total	18,507	22,701
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	100	171
Gross Unrealized Losses, 12 Months or More	1,533	2,070
Gross Unrealized Losses, Total	1,633	2,241
RMBS
Fair Value
Fair Value, Less than 12 Months	2,454	1,456
Fair Value, 12 Months or More	443	2,385
Fair Value, Total	2,897	3,841
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	24	114
Gross Unrealized Losses, 12 Months or More	266	300
Gross Unrealized Losses, Total	290	414
CMBS
Fair Value
Fair Value, Less than 12 Months	1,568	1,024
Fair Value, 12 Months or More	121	1,622
Fair Value, Total	1,689	2,646
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	6	54
Gross Unrealized Losses, 12 Months or More	75	137
Gross Unrealized Losses, Total	81	191
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	1,389	1,371
Fair Value, 12 Months or More	45	1,509
Fair Value, Total	1,434	2,880
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	12	33
Gross Unrealized Losses, 12 Months or More	44	90
Gross Unrealized Losses, Total	$ 56	$ 123