Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Variable Interest Entity [Line Items]
Property and casualty insurance claims and claims expense	$ 10,326	$ 7,822
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Notes payable	123		$ 123
Variable Interest Entity, Primary Beneficiary | Allstate Protection
Variable Interest Entity [Line Items]
Insurance premiums and contract charges	57	42
Property and casualty insurance claims and claims expense	$ 40	$ 34