Reinsurance (Components of Earned Premiums) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premiums Earned, Net [Abstract]
Direct	$ 13,524	$ 12,997	$ 12,001
Assumed	277	288	288
Ceded	5,134	5,110	4,640
Net	8,667	8,175	7,649
Property and casualty
Premiums Earned, Net [Abstract]
Direct	13,097	12,554	11,547
Assumed	231	240	238
Ceded	5,134	5,110	4,640
Net	8,194	7,684	7,145
Long term care
Premiums Earned, Net [Abstract]
Direct	427	443	454
Assumed	46	48	50
Ceded	0	0	0
Net	$ 473	$ 491	$ 504
Percentage of assumed premiums earned to net premiums earned
Premiums Earned, Net [Abstract]
Assumed/ Net %	3.20%	3.50%	3.80%
Percentage of assumed premiums earned to net premiums earned | Property and casualty
Premiums Earned, Net [Abstract]
Assumed/ Net %	2.80%	3.10%	3.30%
Percentage of assumed premiums earned to net premiums earned | Long term care
Premiums Earned, Net [Abstract]
Assumed/ Net %	9.70%	9.80%	9.90%