Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 43,481	$ 42,414
Gross Unrealized Gains	715	1,022
Gross Unrealized Losses	3,040	2,995
Allowance for Credit Losses	45	16	$ 1
Estimated Fair Value	41,111	40,425
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	43,481	42,414
Total fixed maturity securities	41,111	40,425
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	25,839	25,020
Gross Unrealized Gains	423	597
Gross Unrealized Losses	1,305	1,345
Allowance for Credit Losses	13	4	0
Estimated Fair Value	24,944	24,268
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	25,841	25,132
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	7,396	7,713
Gross Unrealized Gains	243	382
Gross Unrealized Losses	835	703
Allowance for Credit Losses	0	0
Estimated Fair Value	6,804	7,392
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	6,804	7,392
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,725	3,411
Gross Unrealized Gains	7	16
Gross Unrealized Losses	488	425
Allowance for Credit Losses	0	0
Estimated Fair Value	3,244	3,002
Commercial mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,830	1,862
Gross Unrealized Gains	11	7
Gross Unrealized Losses	142	230
Allowance for Credit Losses	18	8
Estimated Fair Value	1,681	1,631
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,770	3,515
Gross Unrealized Gains	24	13
Gross Unrealized Losses	239	256
Allowance for Credit Losses	14	4
Estimated Fair Value	3,541	3,268
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,325	8,788
Gross Unrealized Gains	42	36
Gross Unrealized Losses	869	911
Allowance for Credit Losses	32	12	$ 1
Estimated Fair Value	8,466	7,901
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]
Total fixed maturity securities	8,466	7,901
U.S. Treasury and obligations of government-sponsored enterprises
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	220	152
Gross Unrealized Gains	1	1
Gross Unrealized Losses	1	2
Allowance for Credit Losses	0	0
Estimated Fair Value	220	151
Foreign government
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	701	741
Gross Unrealized Gains	6	6
Gross Unrealized Losses	30	34
Allowance for Credit Losses	0	0
Estimated Fair Value	677	713
Redeemable preferred stock
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Allowance for Credit Losses	0	0
Estimated Fair Value	$ 0	$ 0