Investments - Securities available for sale in a loss position (Details) $ in Millions	Jun. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 140,056	$ 173,000
Fair Value, 12 Months or More	48,120	23,486
Fair Value, Total	188,176	196,486
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	20,889	26,605
Gross Unrealized Losses, 12 Months or More	7,942	5,132
Gross Unrealized Losses, Total	$ 28,831	$ 31,737
Number of securities in an unrealized loss position | security	32,032	36,549
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	7,063	4,048
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 5,299	$ 3,493
Fair Value, 12 Months or More	213	1,816
Fair Value, Total	5,512	5,309
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	314	368
Gross Unrealized Losses, 12 Months or More	19	128
Gross Unrealized Losses, Total	333	496
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	7,172	8,697
Fair Value, 12 Months or More	769	73
Fair Value, Total	7,941	8,770
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	861	1,180
Gross Unrealized Losses, 12 Months or More	82	15
Gross Unrealized Losses, Total	943	1,195
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	10,200	10,702
Fair Value, 12 Months or More	438	779
Fair Value, Total	10,638	11,481
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	1,647	1,526
Gross Unrealized Losses, 12 Months or More	18	191
Gross Unrealized Losses, Total	1,665	1,717
Corporate debt
Fair Value
Fair Value, Less than 12 Months	88,949	110,683
Fair Value, 12 Months or More	28,260	13,778
Fair Value, Total	117,209	124,461
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	15,831	19,756
Gross Unrealized Losses, 12 Months or More	5,538	3,609
Gross Unrealized Losses, Total	21,369	23,365
RMBS
Fair Value
Fair Value, Less than 12 Months	8,305	10,953
Fair Value, 12 Months or More	3,775	1,005
Fair Value, Total	12,080	11,958
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	687	1,293
Gross Unrealized Losses, 12 Months or More	560	182
Gross Unrealized Losses, Total	1,247	1,475
CMBS
Fair Value
Fair Value, Less than 12 Months	8,162	11,620
Fair Value, 12 Months or More	4,569	1,728
Fair Value, Total	12,731	13,348
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	851	1,094
Gross Unrealized Losses, 12 Months or More	650	326
Gross Unrealized Losses, Total	1,501	1,420
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	11,969	16,852
Fair Value, 12 Months or More	10,096	4,307
Fair Value, Total	22,065	21,159
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	698	1,388
Gross Unrealized Losses, 12 Months or More	1,075	681
Gross Unrealized Losses, Total	$ 1,773	$ 2,069