Investments - Securities available for sale in a loss position (Details) $ in Millions	Jun. 30, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Fair Value
Fair Value, Less than 12 Months	$ 174,594	$ 58,573
Fair Value, 12 Months or More	14,161	12,293
Fair Value, Total	188,755	70,866
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	19,948	1,137
Gross Unrealized Losses, 12 Months or More	3,329	689
Gross Unrealized Losses, Total	$ 23,277	$ 1,826
Number of securities in an unrealized loss position | security	33,843	15,029
Number of individual securities in continuous unrealized loss position for longer than twelve months | security	4,273	2,644
U.S. government and government sponsored entities
Fair Value
Fair Value, Less than 12 Months	$ 6,962	$ 3,696
Fair Value, 12 Months or More	439	447
Fair Value, Total	7,401	4,143
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	387	14
Gross Unrealized Losses, 12 Months or More	39	13
Gross Unrealized Losses, Total	426	27
Obligations of states, municipalities and political subdivisions
Fair Value
Fair Value, Less than 12 Months	6,802	714
Fair Value, 12 Months or More	99	57
Fair Value, Total	6,901	771
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	641	11
Gross Unrealized Losses, 12 Months or More	28	4
Gross Unrealized Losses, Total	669	15
Non-U.S. governments
Fair Value
Fair Value, Less than 12 Months	9,110	4,644
Fair Value, 12 Months or More	1,658	1,324
Fair Value, Total	10,768	5,968
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	988	115
Gross Unrealized Losses, 12 Months or More	455	132
Gross Unrealized Losses, Total	1,443	247
Corporate debt
Fair Value
Fair Value, Less than 12 Months	109,879	31,914
Fair Value, 12 Months or More	10,125	8,819
Fair Value, Total	120,004	40,733
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	15,019	720
Gross Unrealized Losses, 12 Months or More	2,588	467
Gross Unrealized Losses, Total	17,607	1,187
RMBS
Fair Value
Fair Value, Less than 12 Months	10,351	5,362
Fair Value, 12 Months or More	914	1,154
Fair Value, Total	11,265	6,516
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	809	102
Gross Unrealized Losses, 12 Months or More	123	46
Gross Unrealized Losses, Total	932	148
CMBS
Fair Value
Fair Value, Less than 12 Months	13,057	3,980
Fair Value, 12 Months or More	230	153
Fair Value, Total	13,287	4,133
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	893	63
Gross Unrealized Losses, 12 Months or More	27	16
Gross Unrealized Losses, Total	920	79
CDO/ABS
Fair Value
Fair Value, Less than 12 Months	18,433	8,263
Fair Value, 12 Months or More	696	339
Fair Value, Total	19,129	8,602
Gross Unrealized Losses
Gross Unrealized Losses, Less than 12 Months	1,211	112
Gross Unrealized Losses, 12 Months or More	69	11
Gross Unrealized Losses, Total	$ 1,280	$ 123