Investments - Securities available for sale in a loss position (Details) $ in Millions	Mar. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 146,714	$ 173,000
Fair Value, 12 Months or More	41,057	23,486
Fair Value, Total	187,771	196,486
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	20,649	26,605
Gross Unrealized Losses, 12 Months or More	6,576	5,132
Gross Unrealized Losses, Total	$ 27,225	$ 31,737
Number of securities in an unrealized loss position | security	34,040	36,549
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	5,745	4,048
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 3,573	$ 3,493
Fair Value, 12 Months or More	256	1,816
Fair Value, Total	3,829	5,309
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	275	368
Gross Unrealized Losses, 12 Months or More	14	128
Gross Unrealized Losses, Total	289	496
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	6,907	8,697
Fair Value, 12 Months or More	317	73
Fair Value, Total	7,224	8,770
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	832	1,180
Gross Unrealized Losses, 12 Months or More	25	15
Gross Unrealized Losses, Total	857	1,195
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	10,501	10,702
Fair Value, 12 Months or More	442	779
Fair Value, Total	10,943	11,481
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	1,574	1,526
Gross Unrealized Losses, 12 Months or More	16	191
Gross Unrealized Losses, Total	1,590	1,717
Corporate debt
Fair Value
Fair Value, Less than 12 Months	92,595	110,683
Fair Value, 12 Months or More	25,579	13,778
Fair Value, Total	118,174	124,461
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	15,340	19,756
Gross Unrealized Losses, 12 Months or More	4,739	3,609
Gross Unrealized Losses, Total	20,079	23,365
RMBS
Fair Value
Fair Value, Less than 12 Months	9,238	10,953
Fair Value, 12 Months or More	2,786	1,005
Fair Value, Total	12,024	11,958
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	900	1,293
Gross Unrealized Losses, 12 Months or More	375	182
Gross Unrealized Losses, Total	1,275	1,475
CMBS
Fair Value
Fair Value, Less than 12 Months	10,228	11,620
Fair Value, 12 Months or More	3,333	1,728
Fair Value, Total	13,561	13,348
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	912	1,094
Gross Unrealized Losses, 12 Months or More	494	326
Gross Unrealized Losses, Total	1,406	1,420
CLO/ABS
Fair Value
Fair Value, Less than 12 Months	13,672	16,852
Fair Value, 12 Months or More	8,344	4,307
Fair Value, Total	22,016	21,159
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	816	1,388
Gross Unrealized Losses, 12 Months or More	913	681
Gross Unrealized Losses, Total	$ 1,729	$ 2,069