Investments - Available for Sale Securities in Continuous Unrealized Loss Position (Details) $ in Millions	Mar. 31, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 18,176	$ 21,662
Fair Value, 12 Months or More	15,514	18,751
Fair Value, Total	33,690	40,413
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	374	428
Gross Unrealized Losses, 12 Months or More	2,223	2,655
Gross Unrealized Losses, Total	$ 2,597	$ 3,083
Number of securities in an unrealized loss position | security	10,707	12,274
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	5,239	5,984
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 655	$ 1,718
Fair Value, 12 Months or More	355	358
Fair Value, Total	1,010	2,076
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	7	21
Gross Unrealized Losses, 12 Months or More	71	78
Gross Unrealized Losses, Total	78	99
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	733	1,502
Fair Value, 12 Months or More	582	586
Fair Value, Total	1,315	2,088
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	13	33
Gross Unrealized Losses, 12 Months or More	65	79
Gross Unrealized Losses, Total	78	112
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	1,947	1,964
Fair Value, 12 Months or More	1,749	3,446
Fair Value, Total	3,696	5,410
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	60	55
Gross Unrealized Losses, 12 Months or More	385	534
Gross Unrealized Losses, Total	445	589
Corporate debt
Fair Value
Fair Value, Less than 12 Months	10,136	10,347
Fair Value, 12 Months or More	10,037	10,907
Fair Value, Total	20,173	21,254
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	220	234
Gross Unrealized Losses, 12 Months or More	1,356	1,515
Gross Unrealized Losses, Total	1,576	1,749
RMBS
Fair Value
Fair Value, Less than 12 Months	1,407	3,711
Fair Value, 12 Months or More	1,843	2,147
Fair Value, Total	3,250	5,858
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	42	58
Gross Unrealized Losses, 12 Months or More	272	343
Gross Unrealized Losses, Total	314	401
CMBS
Fair Value
Fair Value, Less than 12 Months	801	1,052
Fair Value, 12 Months or More	650	992
Fair Value, Total	1,451	2,044
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	12	18
Gross Unrealized Losses, 12 Months or More	46	71
Gross Unrealized Losses, Total	58	89
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	2,497	1,368
Fair Value, 12 Months or More	298	315
Fair Value, Total	2,795	1,683
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	20	9
Gross Unrealized Losses, 12 Months or More	28	35
Gross Unrealized Losses, Total	$ 48	$ 44