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, 2024	Dec. 31, 2023	Dec. 31, 2022
Increase (decrease) in claims and claims expense
Incurred	$ 2,900	$ 2,800	$ 2,650
Property and casualty
Increase (decrease) in claims and claims expense
Incurred	39,735	41,070	37,264
Paid	(37,882)	$ (37,973)	$ (32,480)
Property and casualty | Claims incurred and paid from before 2020
Increase (decrease) in claims and claims expense
Incurred	335
Paid	(819)
Auto insurance - liability coverage | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	15,666
Paid	(13,342)
Auto insurance - physical damage coverage | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	8,238
Paid	(8,351)
Homeowners insurance | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	8,157
Paid	(8,201)
Total auto and homeowners insurance | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	32,061
Paid	(29,894)
Other personal lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	2,270
Paid	(1,758)
Commercial lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	616
Paid	(838)
Other business lines | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	310
Paid	(276)
Protection Services | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	547
Paid	(540)
Run-off Property-Liability | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	59
Paid	(89)
Unallocated loss adjustment expenses (“ULAE”) | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	3,480
Paid	(3,443)
Other | Property and casualty
Increase (decrease) in claims and claims expense
Incurred	57
Paid	$ (225)