Reserve for Property and Casualty Insurance Claims and Claims Expense - Prior year reserve reestimates included in claims and claims expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Increase (decrease) in claims and claims expense
Prior years	$ 459	$ 15	$ 604	$ (226)
Auto
Increase (decrease) in claims and claims expense
Prior years	237	(33)	379	(69)
Homeowners
Increase (decrease) in claims and claims expense
Prior years	132	30	122	(173)
Other personal lines
Increase (decrease) in claims and claims expense
Prior years	(2)	1	(9)	(17)
Commercial lines
Increase (decrease) in claims and claims expense
Prior years	92	18	111	33
Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	3	1	4	2
Protection Services
Increase (decrease) in claims and claims expense
Prior years	(3)	(2)	(3)	(2)
Non-catastrophe losses
Increase (decrease) in claims and claims expense
Prior years	408	(22)	566	(20)
Non-catastrophe losses | Auto
Increase (decrease) in claims and claims expense
Prior years	275	(29)	426	(46)
Non-catastrophe losses | Homeowners
Increase (decrease) in claims and claims expense
Prior years	47	(7)	44	(2)
Non-catastrophe losses | Other personal lines
Increase (decrease) in claims and claims expense
Prior years	(5)	(3)	(16)	(3)
Non-catastrophe losses | Commercial lines
Increase (decrease) in claims and claims expense
Prior years	91	18	111	31
Non-catastrophe losses | Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	3	1	4	2
Non-catastrophe losses | Protection Services
Increase (decrease) in claims and claims expense
Prior years	(3)	(2)	(3)	(2)
Catastrophe
Increase (decrease) in claims and claims expense
Prior years	51	37	38	(206)
Catastrophe | Nationwide Aggregate Reinsurance Program
Increase (decrease) in claims and claims expense
Prior years		50		200
Catastrophe | Auto
Increase (decrease) in claims and claims expense
Prior years	(38)	(4)	(47)	(23)
Catastrophe | Homeowners
Increase (decrease) in claims and claims expense
Prior years	85	37	78	(171)
Catastrophe | Other personal lines
Increase (decrease) in claims and claims expense
Prior years	3	4	7	(14)
Catastrophe | Commercial lines
Increase (decrease) in claims and claims expense
Prior years	1	0	0	2
Catastrophe | Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	0	0	0	0
Catastrophe | Protection Services
Increase (decrease) in claims and claims expense
Prior years	$ 0	$ 0	$ 0	0
Fire | Southern California Edison
Increase (decrease) in claims and claims expense
Prior years				$ 110