Reserve for Property and Casualty Insurance Claims and Claims Expense - Schedule of Reconciliation of Total Claims and Claims Expense Incurred and Paid by Coverage (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Increase (decrease) in claims and claims expense
Incurred	$ 41,070	$ 37,264	$ 29,318
Property and casualty
Increase (decrease) in claims and claims expense
Incurred	41,070
Paid	(37,973)	$ (32,480)	$ (28,245)
Property and casualty | Claims incurred and paid from before 2019
Increase (decrease) in claims and claims expense
Incurred	243
Paid	(845)
Auto insurance - liability coverage | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	15,752
Paid	(13,032)
Auto insurance - physical damage coverage | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	9,128
Paid	(9,290)
Homeowners insurance | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	9,330
Paid	(8,225)
Total auto and homeowners insurance | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	34,210
Paid	(30,547)
Other personal lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	1,827
Paid	(1,632)
Commercial lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	784
Paid	(951)
Other business lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	148
Paid	(206)
Protection Services | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	533
Paid	(522)
Run-off Property-Liability | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	78
Paid	(89)
Unallocated loss adjustment expenses (“ULAE”) | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	3,292
Paid	(3,269)
Other | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	(45)
Paid	$ 88