Reinsurance (Components of Earned Premiums) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Premiums Earned, Net [Abstract]
Direct	$ 15,357	$ 15,025	$ 14,315
Assumed	293	293	267
Ceded	4,750	5,107	5,102
Net	10,900	10,211	9,480
Property and casualty
Premiums Earned, Net [Abstract]
Direct	14,974	14,629	13,908
Assumed	253	252	223
Ceded	4,750	5,107	5,102
Net	10,477	9,774	9,029
Long-term care
Premiums Earned, Net [Abstract]
Direct	383	396	407
Assumed	40	41	44
Ceded	0	0	0
Net	$ 423	$ 437	$ 451
Percentage of assumed premiums earned to net premiums earned
Premiums Earned, Net [Abstract]
Assumed/ Net %	2.70%	2.90%	2.80%
Percentage of assumed premiums earned to net premiums earned | Property and casualty
Premiums Earned, Net [Abstract]
Assumed/ Net %	2.40%	2.60%	2.50%
Percentage of assumed premiums earned to net premiums earned | Long-term care
Premiums Earned, Net [Abstract]
Assumed/ Net %	9.50%	9.40%	9.80%