Investments - Available for Sale Securities in Continuous Unrealized Loss Position (Details) $ in Millions	Mar. 31, 2026 USD ($) security	Dec. 31, 2025 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 23,761	$ 10,186
Fair Value, 12 Months or More	12,489	12,868
Fair Value, Total	36,250	23,054
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	397	193
Gross Unrealized Losses, 12 Months or More	1,700	1,675
Gross Unrealized Losses, Total	$ 2,097	$ 1,868
Number of securities in an unrealized loss position | security	10,977	7,526
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	4,249	4,065
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 645	$ 167
Fair Value, 12 Months or More	305	322
Fair Value, Total	950	489
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	8	8
Gross Unrealized Losses, 12 Months or More	80	78
Gross Unrealized Losses, Total	88	86
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	283	232
Fair Value, 12 Months or More	541	515
Fair Value, Total	824	747
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	5	8
Gross Unrealized Losses, 12 Months or More	47	45
Gross Unrealized Losses, Total	52	53
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	2,147	1,524
Fair Value, 12 Months or More	1,503	1,347
Fair Value, Total	3,650	2,871
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	46	33
Gross Unrealized Losses, 12 Months or More	349	336
Gross Unrealized Losses, Total	395	369
Corporate debt
Fair Value
Fair Value, Less than 12 Months	13,598	6,031
Fair Value, 12 Months or More	7,786	8,165
Fair Value, Total	21,384	14,196
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	279	125
Gross Unrealized Losses, 12 Months or More	938	927
Gross Unrealized Losses, Total	1,217	1,052
RMBS
Fair Value
Fair Value, Less than 12 Months	3,376	769
Fair Value, 12 Months or More	1,645	1,764
Fair Value, Total	5,021	2,533
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	33	8
Gross Unrealized Losses, 12 Months or More	255	241
Gross Unrealized Losses, Total	288	249
CMBS
Fair Value
Fair Value, Less than 12 Months	1,283	580
Fair Value, 12 Months or More	529	523
Fair Value, Total	1,812	1,103
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	12	6
Gross Unrealized Losses, 12 Months or More	24	30
Gross Unrealized Losses, Total	36	36
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	2,429	883
Fair Value, 12 Months or More	180	232
Fair Value, Total	2,609	1,115
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	14	5
Gross Unrealized Losses, 12 Months or More	7	18
Gross Unrealized Losses, Total	$ 21	$ 23