Investments (Securities in a gross unrealized loss position) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	$ 25,234	$ 5,695
Gross Unrealized Losses, Less than 12 Months	2,946	92
Estimated Fair Value, 12 Months or Longer	4,277	370
Gross Unrealized Losses, 12 Months or Longer	1,110	20
Estimated Fair Value, Total	29,511	6,065
Gross Unrealized Losses, Total	4,056	112
Corporate and other bonds
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	15,946	2,389
Gross Unrealized Losses, Less than 12 Months	1,585	48
Estimated Fair Value, 12 Months or Longer	1,634	136
Gross Unrealized Losses, 12 Months or Longer	424	8
Estimated Fair Value, Total	17,580	2,525
Gross Unrealized Losses, Total	2,009	56
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	4,079	730
Gross Unrealized Losses, Less than 12 Months	769	14
Estimated Fair Value, 12 Months or Longer	456	0
Gross Unrealized Losses, 12 Months or Longer	170	0
Estimated Fair Value, Total	4,535	730
Gross Unrealized Losses, Total	939	14
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,406	1,043
Gross Unrealized Losses, Less than 12 Months	144	8
Estimated Fair Value, 12 Months or Longer	1,143	0
Gross Unrealized Losses, 12 Months or Longer	303	0
Estimated Fair Value, Total	2,549	1,043
Gross Unrealized Losses, Total	447	8
Commercial mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,167	527
Gross Unrealized Losses, Less than 12 Months	159	7
Estimated Fair Value, 12 Months or Longer	408	167
Gross Unrealized Losses, 12 Months or Longer	96	12
Estimated Fair Value, Total	1,575	694
Gross Unrealized Losses, Total	255	19
Other asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,087	840
Gross Unrealized Losses, Less than 12 Months	262	10
Estimated Fair Value, 12 Months or Longer	542	62
Gross Unrealized Losses, 12 Months or Longer	99	0
Estimated Fair Value, Total	2,629	902
Gross Unrealized Losses, Total	361	10
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	4,660	2,410
Gross Unrealized Losses, Less than 12 Months	565	25
Estimated Fair Value, 12 Months or Longer	2,093	229
Gross Unrealized Losses, 12 Months or Longer	498	12
Estimated Fair Value, Total	6,753	2,639
Gross Unrealized Losses, Total	1,063	37
U.S. Treasury and obligations of government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	76	69
Gross Unrealized Losses, Less than 12 Months	1	3
Estimated Fair Value, 12 Months or Longer	16	5
Gross Unrealized Losses, 12 Months or Longer	1	0
Estimated Fair Value, Total	92	74
Gross Unrealized Losses, Total	2	3
Foreign government
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	473	97
Gross Unrealized Losses, Less than 12 Months	26	2
Estimated Fair Value, 12 Months or Longer	78	0
Gross Unrealized Losses, 12 Months or Longer	17	0
Estimated Fair Value, Total	551	97
Gross Unrealized Losses, Total	$ 43	$ 2