Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fixed maturity securities:
Total fixed maturity securities	$ 44,910	$ 44,631
Equity securities:
Equity securities	1,033	992
Short term and other	1,336	1,789
Total assets	47,279	47,412
Other liabilities	14	19
Total liabilities	14	19
Corporate and other bonds
Fixed maturity securities:
Total fixed maturity securities	25,068	25,234
States, municipalities and political subdivisions
Fixed maturity securities:
Total fixed maturity securities	11,866	11,592
Asset-backed
Fixed maturity securities:
Total fixed maturity securities	7,976	7,805
Common Stock
Equity securities:
Equity securities	214	195
Non-redeemable preferred stock
Equity securities:
Equity securities	819	797
Level 1
Fixed maturity securities:
Total fixed maturity securities	158	355
Equity securities:
Equity securities	265	243
Short term and other	1,310	1,761
Total assets	1,733	2,359
Other liabilities	0	0
Total liabilities	0	0
Level 1 | Corporate and other bonds
Fixed maturity securities:
Total fixed maturity securities	158	355
Level 1 | States, municipalities and political subdivisions
Fixed maturity securities:
Total fixed maturity securities	0	0
Level 1 | Asset-backed
Fixed maturity securities:
Total fixed maturity securities	0	0
Level 1 | Common Stock
Equity securities:
Equity securities	198	175
Level 1 | Non-redeemable preferred stock
Equity securities:
Equity securities	67	68
Level 2
Fixed maturity securities:
Total fixed maturity securities	43,402	43,152
Equity securities:
Equity securities	743	722
Short term and other	26	28
Total assets	44,171	43,902
Other liabilities	14	19
Total liabilities	14	19
Level 2 | Corporate and other bonds
Fixed maturity securities:
Total fixed maturity securities	24,027	24,109
Level 2 | States, municipalities and political subdivisions
Fixed maturity securities:
Total fixed maturity securities	11,809	11,546
Level 2 | Asset-backed
Fixed maturity securities:
Total fixed maturity securities	7,566	7,497
Level 2 | Common Stock
Equity securities:
Equity securities	0	0
Level 2 | Non-redeemable preferred stock
Equity securities:
Equity securities	743	722
Level 3
Fixed maturity securities:
Total fixed maturity securities	1,350	1,124
Equity securities:
Equity securities	25	27
Short term and other	0	0
Total assets	1,375	1,151
Other liabilities	0	0
Total liabilities	0	0
Level 3 | Corporate and other bonds
Fixed maturity securities:
Total fixed maturity securities	883	770
Level 3 | States, municipalities and political subdivisions
Fixed maturity securities:
Total fixed maturity securities	57	46
Level 3 | Asset-backed
Fixed maturity securities:
Total fixed maturity securities	410	308
Level 3 | Common Stock
Equity securities:
Equity securities	16	20
Level 3 | Non-redeemable preferred stock
Equity securities:
Equity securities	$ 9	$ 7