Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Fixed maturity securities:
Fixed maturity securities	$ 43,882	$ 43,402
Equity securities:
Equity securities	793	769
Short-term and other	1,549	2,137
Total assets	46,224	46,308
Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	26,213	26,250
States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	8,835	8,431
Asset-backed
Fixed maturity securities:
Fixed maturity securities	8,834	8,721
Common Stock
Equity securities:
Equity securities	249	237
Non-redeemable preferred stock
Equity securities:
Equity securities	544	532
Level 1
Fixed maturity securities:
Fixed maturity securities	243	238
Equity securities:
Equity securities	273	259
Short-term and other	1,503	2,086
Total assets	2,019	2,583
Level 1 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	243	238
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	239	224
Level 1 | Non-redeemable preferred stock
Equity securities:
Equity securities	34	35
Level 2
Fixed maturity securities:
Fixed maturity securities	41,058	40,638
Equity securities:
Equity securities	510	497
Short-term and other	46	51
Total assets	41,614	41,186
Level 2 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	24,376	24,529
Level 2 | States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	8,791	8,386
Level 2 | Asset-backed
Fixed maturity securities:
Fixed maturity securities	7,891	7,723
Level 2 | Common Stock
Equity securities:
Equity securities	0	0
Level 2 | Non-redeemable preferred stock
Equity securities:
Equity securities	510	497
Level 3
Fixed maturity securities:
Fixed maturity securities	2,581	2,526
Equity securities:
Equity securities	10	13
Short-term and other	0	0
Total assets	2,591	2,539
Level 3 | Corporate and other bonds
Fixed maturity securities:
Fixed maturity securities	1,594	1,483
Level 3 | States, municipalities and political subdivisions
Fixed maturity securities:
Fixed maturity securities	44	45
Level 3 | Asset-backed
Fixed maturity securities:
Fixed maturity securities	943	998
Level 3 | Common Stock
Equity securities:
Equity securities	10	13
Level 3 | Non-redeemable preferred stock
Equity securities:
Equity securities	$ 0	$ 0