Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 42,414	$ 41,032
Gross Unrealized Gains	1,022	652
Gross Unrealized Losses	2,995	4,056
Allowance for Credit Losses	16	1		$ 18
Estimated Fair Value	40,425	37,627
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities trading	0	0
Total fixed maturity securities trading	0	0
Debt securities, amortized cost	42,414	41,032
Total fixed maturity securities	40,425	37,627	[1]
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	25,020	23,137
Gross Unrealized Gains	597	301
Gross Unrealized Losses	1,345	2,009
Allowance for Credit Losses	4	0		11
Estimated Fair Value	24,268	21,429
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	25,132	22,117
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	7,713	8,918
Gross Unrealized Gains	382	338
Gross Unrealized Losses	703	939
Allowance for Credit Losses	0	0
Estimated Fair Value	7,392	8,317
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	7,392	8,317
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,411	3,073
Gross Unrealized Gains	16	5
Gross Unrealized Losses	425	447
Allowance for Credit Losses	0	0
Estimated Fair Value	3,002	2,631
Commercial mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,862	1,886
Gross Unrealized Gains	7	4
Gross Unrealized Losses	230	255
Allowance for Credit Losses	8	0
Estimated Fair Value	1,631	1,635
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,515	3,287
Gross Unrealized Gains	13	2
Gross Unrealized Losses	256	361
Allowance for Credit Losses	4	1
Estimated Fair Value	3,268	2,927
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	8,788	8,246
Gross Unrealized Gains	36	11
Gross Unrealized Losses	911	1,063
Allowance for Credit Losses	12	1		$ 7
Estimated Fair Value	7,901	7,193
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	7,901	7,193
U.S. Treasury and obligations of government-sponsored enterprises
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	152	111
Gross Unrealized Gains	1	1
Gross Unrealized Losses	2	2
Allowance for Credit Losses	0	0
Estimated Fair Value	151	110
Foreign government
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	741	617
Gross Unrealized Gains	6	1
Gross Unrealized Losses	34	43
Allowance for Credit Losses	0	0
Estimated Fair Value	713	575
Redeemable preferred stock
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	0	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Allowance for Credit Losses	0	0
Estimated Fair Value	$ 0	$ 3

[1] As of January 1, 2023, the Company adopted ASU 2018-12, Financial Services-Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts (ASU 2018-12) using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Consolidated Financial Statements for additional information.