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, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Claims Development [Line Items]
Reserve for property and casualty insurance claims and claims expense	$ 41,917	$ 39,858
Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	33,315
ULAE	1,709
Recoverables	8,602	8,396	$ 9,176	$ 9,479
ULAE	40
Reserve for property and casualty insurance claims and claims expense	41,917	$ 39,858	$ 37,541	$ 33,060
Auto insurance - liability coverage
Claims Development [Line Items]
Net outstanding liabilities	21,182
Auto insurance - liability coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	21,182
Recoverables	6,958
Auto insurance - physical damage coverage
Claims Development [Line Items]
Net outstanding liabilities	721
Auto insurance - physical damage coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	721
Recoverables	37
Homeowners insurance
Claims Development [Line Items]
Net outstanding liabilities	4,266
Homeowners insurance | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	4,266
Recoverables	523
Other personal lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	2,266
Recoverables	260
Commercial lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,654
Recoverables	299
Other business lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	133
Recoverables	2
Protection Services | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	53
Recoverables	15
Run-off Property-Liability
Claims Development [Line Items]
Reserve for property and casualty insurance claims and claims expense	723
Run-off Property-Liability | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,328
Recoverables	468
Other | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	$ 3