Investments - Available for Sale Securities in Continuous Unrealized Loss Position (Details) $ in Millions	Dec. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 21,662	$ 11,248
Fair Value, 12 Months or More	18,751	31,037
Fair Value, Total	40,413	42,285
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	428	493
Gross Unrealized Losses, 12 Months or More	2,655	3,392
Gross Unrealized Losses, Total	$ 3,083	$ 3,885
Number of securities in an unrealized loss position | security	12,274	13,052
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	5,984	10,027
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 1,718	$ 1,027
Fair Value, 12 Months or More	358	804
Fair Value, Total	2,076	1,831
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	21	10
Gross Unrealized Losses, 12 Months or More	78	79
Gross Unrealized Losses, Total	99	89
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	1,502	850
Fair Value, 12 Months or More	586	1,602
Fair Value, Total	2,088	2,452
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	33	24
Gross Unrealized Losses, 12 Months or More	79	133
Gross Unrealized Losses, Total	112	157
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	1,964	1,431
Fair Value, 12 Months or More	3,446	4,503
Fair Value, Total	5,410	5,934
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	55	87
Gross Unrealized Losses, 12 Months or More	534	583
Gross Unrealized Losses, Total	589	670
Corporate debt
Fair Value
Fair Value, Less than 12 Months	10,347	4,089
Fair Value, 12 Months or More	10,907	18,612
Fair Value, Total	21,254	22,701
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	234	171
Gross Unrealized Losses, 12 Months or More	1,515	2,070
Gross Unrealized Losses, Total	1,749	2,241
RMBS
Fair Value
Fair Value, Less than 12 Months	3,711	1,456
Fair Value, 12 Months or More	2,147	2,385
Fair Value, Total	5,858	3,841
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	58	114
Gross Unrealized Losses, 12 Months or More	343	300
Gross Unrealized Losses, Total	401	414
CMBS
Fair Value
Fair Value, Less than 12 Months	1,052	1,024
Fair Value, 12 Months or More	992	1,622
Fair Value, Total	2,044	2,646
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	18	54
Gross Unrealized Losses, 12 Months or More	71	137
Gross Unrealized Losses, Total	89	191
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	1,368	1,371
Fair Value, 12 Months or More	315	1,509
Fair Value, Total	1,683	2,880
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	9	33
Gross Unrealized Losses, 12 Months or More	35	90
Gross Unrealized Losses, Total	$ 44	$ 123