Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fixed maturity securities:
Fixed maturity securities	$ 40,403	$ 40,425
Equity securities:
Equity securities	669	683
Short-term and other	1,571	2,008
Total assets	42,643	43,116
Other liabilities	0	1
Total liabilities	0	1
Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	25,269	25,132
States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	7,029	7,392
Asset-backed
Fixed maturity securities:
Fixed maturity securities	8,105	7,901
Common Stock
Equity securities:
Equity securities	180	191
Non-redeemable preferred stock
Equity securities:
Equity securities	489	492
Level 1
Fixed maturity securities:
Fixed maturity securities	194	161
Equity securities:
Equity securities	213	219
Short-term and other	1,546	1,976
Total assets	1,953	2,356
Other liabilities	0	0
Total liabilities	0	0
Level 1 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	194	161
Level 1 | States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	0	0
Level 1 | Asset-backed
Fixed maturity securities:
Fixed maturity securities	0	0
Level 1 | Common Stock
Equity securities:
Equity securities	168	167
Level 1 | Non-redeemable preferred stock
Equity securities:
Equity securities	45	52
Level 2
Fixed maturity securities:
Fixed maturity securities	38,150	38,274
Equity securities:
Equity securities	442	440
Short-term and other	25	32
Total assets	38,617	38,746
Other liabilities	0	1
Total liabilities	0	1
Level 2 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	23,946	23,926
Level 2 | States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	6,986	7,348
Level 2 | Asset-backed
Fixed maturity securities:
Fixed maturity securities	7,218	7,000
Level 2 | Common Stock
Equity securities:
Equity securities	0	0
Level 2 | Non-redeemable preferred stock
Equity securities:
Equity securities	442	440
Level 3
Fixed maturity securities:
Fixed maturity securities	2,059	1,990
Equity securities:
Equity securities	14	24
Short-term and other	0	0
Total assets	2,073	2,014
Other liabilities	0	0
Total liabilities	0	0
Level 3 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	1,129	1,045
Level 3 | States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	43	44
Level 3 | Asset-backed
Fixed maturity securities:
Fixed maturity securities	887	901
Level 3 | Common Stock
Equity securities:
Equity securities	12	24
Level 3 | Non-redeemable preferred stock
Equity securities:
Equity securities	$ 2	$ 0