Investments - Available for Sale Securities in Continuous Unrealized Loss Position (Details) $ in Millions	Mar. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 35,639	$ 34,407
Fair Value, 12 Months or More	134,235	136,774
Fair Value, Total	169,874	171,181
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	2,869	2,958
Gross Unrealized Losses, 12 Months or More	22,475	21,333
Gross Unrealized Losses, Total	$ 25,344	$ 24,291
Number of securities in an unrealized loss position | security	27,875	27,930
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	22,726	22,663
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 2,600	$ 1,046
Fair Value, 12 Months or More	1,486	1,550
Fair Value, Total	4,086	2,596
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	33	12
Gross Unrealized Losses, 12 Months or More	358	315
Gross Unrealized Losses, Total	391	327
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	2,150	1,994
Fair Value, 12 Months or More	5,187	5,218
Fair Value, Total	7,337	7,212
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	134	133
Gross Unrealized Losses, 12 Months or More	752	709
Gross Unrealized Losses, Total	886	842
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	2,007	1,901
Fair Value, 12 Months or More	7,424	7,483
Fair Value, Total	9,431	9,384
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	148	168
Gross Unrealized Losses, 12 Months or More	1,302	1,175
Gross Unrealized Losses, Total	1,450	1,343
Corporate debt
Fair Value
Fair Value, Less than 12 Months	16,567	15,483
Fair Value, 12 Months or More	91,020	93,649
Fair Value, Total	107,587	109,132
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	2,141	1,936
Gross Unrealized Losses, 12 Months or More	16,952	16,076
Gross Unrealized Losses, Total	19,093	18,012
RMBS
Fair Value
Fair Value, Less than 12 Months	4,044	4,154
Fair Value, 12 Months or More	7,877	7,246
Fair Value, Total	11,921	11,400
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	189	288
Gross Unrealized Losses, 12 Months or More	1,025	880
Gross Unrealized Losses, Total	1,214	1,168
CMBS
Fair Value
Fair Value, Less than 12 Months	1,678	2,864
Fair Value, 12 Months or More	8,664	8,192
Fair Value, Total	10,342	11,056
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	70	219
Gross Unrealized Losses, 12 Months or More	1,050	1,027
Gross Unrealized Losses, Total	1,120	1,246
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	6,593	6,965
Fair Value, 12 Months or More	12,577	13,436
Fair Value, Total	19,170	20,401
Gross Unrealized Losses*
Gross Unrealized Losses, Less than 12 Months	154	202
Gross Unrealized Losses, 12 Months or More	1,036	1,151
Gross Unrealized Losses, Total	$ 1,190	$ 1,353