Variable Interest Entities - (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Fixed income securities, at fair value, amortized cost (in dollars)	$ 41,344	$ 41,344	$ 40,034
Short-term, at fair value, amortized cost (in dollars)	5,516	5,516	$ 6,807
Variable Interest Entity, Primary Beneficiary | Allstate Protection
Variable Interest Entity [Line Items]
Property and casualty insurance premiums	$ 45	$ 90