Reserve for Property and Casualty Insurance Claims and Claims Expense - Schedule of Reconciliation of the Net Incurred and Paid Claims Development to Reserve for Property and Casualty Insurance Claims and Claims Expense (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	$ 31,462
ULAE	1,679
Recoverables	8,396	$ 9,176	$ 9,479	$ 7,033
ULAE	70
Gross reserve for property and casualty insurance claims and claims expense	39,858	$ 37,541	$ 33,060	$ 27,610
Auto insurance - liability coverage
Claims Development [Line Items]
Net outstanding liabilities	19,524
Auto insurance - liability coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	19,524
Recoverables	6,880
Auto insurance - physical damage coverage
Claims Development [Line Items]
Net outstanding liabilities	844
Auto insurance - physical damage coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	844
Recoverables	22
Homeowners insurance
Claims Development [Line Items]
Net outstanding liabilities	4,450
Homeowners insurance | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	4,450
Recoverables	343
Other personal lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,788
Recoverables	243
Commercial lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,745
Recoverables	326
Other business lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	17
Recoverables	1
Protection Services | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	46
Recoverables	14
Run-off Property-Liability
Claims Development [Line Items]
Gross reserve for property and casualty insurance claims and claims expense	762
Run-off Property-Liability | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,361
Recoverables	497
Other | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	$ 8