Reserve for Property and Casualty Insurance Claims and Claims Expense - Reconciliation of the net incurred and paid claims development (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	$ 23,581
ULAE	1,430
Recoverables	9,479	$ 7,033
ULAE	196
Gross reserve for property and casualty insurance claims and claims expense	33,060	$ 27,610	$ 27,712	$ 27,423
Auto insurance - liability coverage
Claims Development [Line Items]
Net outstanding liabilities	14,955
Auto insurance - liability coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	14,955
Recoverables	7,247
Auto insurance - physical damage coverage
Claims Development [Line Items]
Net outstanding liabilities	435
Auto insurance - physical damage coverage | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	435
Recoverables	81
Homeowners insurance
Claims Development [Line Items]
Net outstanding liabilities	2,574
Homeowners insurance | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	2,574
Recoverables	1,023
Other personal lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,316
Recoverables	173
Commercial lines | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,316
Recoverables	256
Protection Services | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	33
Recoverables	9
Run-off Property-Liability
Claims Development [Line Items]
Gross reserve for property and casualty insurance claims and claims expense	733
Run-off Property-Liability | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	1,342
Recoverables	494
Other (2) | Property and casualty
Claims Development [Line Items]
Net outstanding liabilities	$ 180