Investments (Securities in a gross unrealized loss position) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	$ 5,695	$ 1,666
Gross Unrealized Losses, Less than 12 Months	92	74
Estimated Fair Value, 12 Months or Longer	370	64
Gross Unrealized Losses, 12 Months or Longer	20	3
Estimated Fair Value, Total	6,065	1,730
Gross Unrealized Losses, Total	112	77
Corporate and other bonds
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,389	609
Gross Unrealized Losses, Less than 12 Months	48	21
Estimated Fair Value, 12 Months or Longer	136	12
Gross Unrealized Losses, 12 Months or Longer	8	1
Estimated Fair Value, Total	2,525	621
Gross Unrealized Losses, Total	56	22
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	730	33
Gross Unrealized Losses, Less than 12 Months	14	0
Estimated Fair Value, 12 Months or Longer	0	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	730	33
Gross Unrealized Losses, Total	14
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,043	71
Gross Unrealized Losses, Less than 12 Months	8	1
Estimated Fair Value, 12 Months or Longer	0	11
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	1,043	82
Gross Unrealized Losses, Total	8	1
Commercial mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	527	533
Gross Unrealized Losses, Less than 12 Months	7	40
Estimated Fair Value, 12 Months or Longer	167	28
Gross Unrealized Losses, 12 Months or Longer	12	2
Estimated Fair Value, Total	694	561
Gross Unrealized Losses, Total	19	42
Other asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	840	344
Gross Unrealized Losses, Less than 12 Months	10	9
Estimated Fair Value, 12 Months or Longer	62	13
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	902	357
Gross Unrealized Losses, Total	10	9
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,410	948
Gross Unrealized Losses, Less than 12 Months	25	50
Estimated Fair Value, 12 Months or Longer	229	52
Gross Unrealized Losses, 12 Months or Longer	12	2
Estimated Fair Value, Total	2,639	1,000
Gross Unrealized Losses, Total	37	52
U.S. Treasury and obligations of government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	69	63
Gross Unrealized Losses, Less than 12 Months	3	3
Estimated Fair Value, 12 Months or Longer	5	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	74	63
Gross Unrealized Losses, Total	3	3
Foreign government
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	97	13
Gross Unrealized Losses, Less than 12 Months	2	0
Estimated Fair Value, 12 Months or Longer	0	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	97	13
Gross Unrealized Losses, Total	$ 2	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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