Investments (Securities in a gross unrealized loss position) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	$ 15,913	$ 5,695
Gross Unrealized Losses, Less than 12 Months	1,086	92
Estimated Fair Value, 12 Months or Longer	611	370
Gross Unrealized Losses, 12 Months or Longer	71	20
Estimated Fair Value, Total	16,524	6,065
Gross Unrealized Losses, Total	1,157	112
Corporate and other bonds
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	7,390	2,389
Gross Unrealized Losses, Less than 12 Months	441	48
Estimated Fair Value, 12 Months or Longer	327	136
Gross Unrealized Losses, 12 Months or Longer	45	8
Estimated Fair Value, Total	7,717	2,525
Gross Unrealized Losses, Total	486	56
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,796	730
Gross Unrealized Losses, Less than 12 Months	314	14
Estimated Fair Value, 12 Months or Longer	35	0
Gross Unrealized Losses, 12 Months or Longer	5	0
Estimated Fair Value, Total	2,831	730
Gross Unrealized Losses, Total	319	14
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,315	1,043
Gross Unrealized Losses, Less than 12 Months	160	8
Estimated Fair Value, 12 Months or Longer	0	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	2,315	1,043
Gross Unrealized Losses, Total	160	8
Commercial mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,274	527
Gross Unrealized Losses, Less than 12 Months	65	7
Estimated Fair Value, 12 Months or Longer	151	167
Gross Unrealized Losses, 12 Months or Longer	16	12
Estimated Fair Value, Total	1,425	694
Gross Unrealized Losses, Total	81	19
Other asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,717	840
Gross Unrealized Losses, Less than 12 Months	90	10
Estimated Fair Value, 12 Months or Longer	67	62
Gross Unrealized Losses, 12 Months or Longer	3	0
Estimated Fair Value, Total	1,784	902
Gross Unrealized Losses, Total	93	10
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	5,306	2,410
Gross Unrealized Losses, Less than 12 Months	315	25
Estimated Fair Value, 12 Months or Longer	218	229
Gross Unrealized Losses, 12 Months or Longer	19	12
Estimated Fair Value, Total	5,524	2,639
Gross Unrealized Losses, Total	334	37
U.S. Treasury and obligations of government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	94	69
Gross Unrealized Losses, Less than 12 Months	5	3
Estimated Fair Value, 12 Months or Longer	5	5
Gross Unrealized Losses, 12 Months or Longer	0	0
Estimated Fair Value, Total	99	74
Gross Unrealized Losses, Total	5	3
Foreign government
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	327	97
Gross Unrealized Losses, Less than 12 Months	11	2
Estimated Fair Value, 12 Months or Longer	26	0
Gross Unrealized Losses, 12 Months or Longer	2	0
Estimated Fair Value, Total	353	97
Gross Unrealized Losses, Total	$ 13	$ 2

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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