Reserve for Property and Casualty Insurance Claims and Claims Expense - Prior year reserve reestimates included in claims and claims expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Increase (decrease) in claims and claims expense
Prior years	$ 1,741	$ 122	$ (436)
Auto
Increase (decrease) in claims and claims expense
Prior years	1,185	149	(107)
Homeowners
Increase (decrease) in claims and claims expense
Prior years	194	(153)	(439)
Other personal lines
Increase (decrease) in claims and claims expense
Prior years	(32)	(107)	(66)
Commercial lines
Increase (decrease) in claims and claims expense
Prior years	272	119	36
Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	125	116	141
Protection Services
Increase (decrease) in claims and claims expense
Prior years	(3)	(2)	(1)
Catastrophe losses
Increase (decrease) in claims and claims expense
Prior years	18	(202)	(503)
Catastrophe losses | Nationwide Aggregate Reinsurance Program
Increase (decrease) in claims and claims expense
Prior years		240
Catastrophe losses | PG&E And Southern California Edison
Increase (decrease) in claims and claims expense
Prior years			495
Catastrophe losses | Auto
Increase (decrease) in claims and claims expense
Prior years	(64)	(29)	(44)
Catastrophe losses | Homeowners
Increase (decrease) in claims and claims expense
Prior years	81	(165)	(422)
Catastrophe losses | Other personal lines
Increase (decrease) in claims and claims expense
Prior years	2	(11)	(39)
Catastrophe losses | Commercial lines
Increase (decrease) in claims and claims expense
Prior years	(1)	3	2
Catastrophe losses | Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	0	0	0
Catastrophe losses | Protection Services
Increase (decrease) in claims and claims expense
Prior years	0	0	0
Fire | Southern California Edison
Increase (decrease) in claims and claims expense
Prior years		110
Non-catastrophe losses
Increase (decrease) in claims and claims expense
Prior years	1,723	324	67
Non-catastrophe losses | Auto
Increase (decrease) in claims and claims expense
Prior years	1,249	178	(63)
Non-catastrophe losses | Homeowners
Increase (decrease) in claims and claims expense
Prior years	113	12	(17)
Non-catastrophe losses | Other personal lines
Increase (decrease) in claims and claims expense
Prior years	(34)	(96)	(27)
Non-catastrophe losses | Commercial lines
Increase (decrease) in claims and claims expense
Prior years	273	116	34
Non-catastrophe losses | Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	125	116	141
Non-catastrophe losses | Protection Services
Increase (decrease) in claims and claims expense
Prior years	(3)	(2)	(1)
Annual reserve review | Run-off Property-Liability
Increase (decrease) in claims and claims expense
Prior years	$ 118	$ 111	$ 132