Investments (Securities in a gross unrealized loss position) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	$ 15,037	$ 25,234
Gross Unrealized Losses, Less than 12 Months	790	2,946
Estimated Fair Value, 12 Months or Longer	13,229	4,277
Gross Unrealized Losses, 12 Months or Longer	2,628	1,110
Estimated Fair Value, Total	28,266	29,511
Gross Unrealized Losses, Total	3,418	4,056
Corporate and other bonds
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	10,753	15,946
Gross Unrealized Losses, Less than 12 Months	545	1,585
Estimated Fair Value, 12 Months or Longer	6,184	1,634
Gross Unrealized Losses, 12 Months or Longer	1,130	424
Estimated Fair Value, Total	16,937	17,580
Gross Unrealized Losses, Total	1,675	2,009
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,708	4,079
Gross Unrealized Losses, Less than 12 Months	87	769
Estimated Fair Value, 12 Months or Longer	2,347	456
Gross Unrealized Losses, 12 Months or Longer	654	170
Estimated Fair Value, Total	4,055	4,535
Gross Unrealized Losses, Total	741	939
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	2,288	4,660
Gross Unrealized Losses, Less than 12 Months	150	565
Estimated Fair Value, 12 Months or Longer	4,330	2,093
Gross Unrealized Losses, 12 Months or Longer	811	498
Estimated Fair Value, Total	6,618	6,753
Gross Unrealized Losses, Total	961	1,063
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	741	1,406
Gross Unrealized Losses, Less than 12 Months	28	144
Estimated Fair Value, 12 Months or Longer	1,784	1,143
Gross Unrealized Losses, 12 Months or Longer	385	303
Estimated Fair Value, Total	2,525	2,549
Gross Unrealized Losses, Total	413	447
Commercial mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	474	1,167
Gross Unrealized Losses, Less than 12 Months	36	159
Estimated Fair Value, 12 Months or Longer	1,072	408
Gross Unrealized Losses, 12 Months or Longer	206	96
Estimated Fair Value, Total	1,546	1,575
Gross Unrealized Losses, Total	242	255
Other asset-backed
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,073	2,087
Gross Unrealized Losses, Less than 12 Months	86	262
Estimated Fair Value, 12 Months or Longer	1,474	542
Gross Unrealized Losses, 12 Months or Longer	220	99
Estimated Fair Value, Total	2,547	2,629
Gross Unrealized Losses, Total	306	361
U.S. Treasury and obligations of government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	57	76
Gross Unrealized Losses, Less than 12 Months	1	1
Estimated Fair Value, 12 Months or Longer	41	16
Gross Unrealized Losses, 12 Months or Longer	1	1
Estimated Fair Value, Total	98	92
Gross Unrealized Losses, Total	2	2
Foreign government
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	231	473
Gross Unrealized Losses, Less than 12 Months	7	26
Estimated Fair Value, 12 Months or Longer	327	78
Gross Unrealized Losses, 12 Months or Longer	32	17
Estimated Fair Value, Total	558	551
Gross Unrealized Losses, Total	$ 39	$ 43

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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