Variable Interest Entities - (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Fixed income securities, at fair value, amortized cost (in dollars)	$ 39,437	$ 40,034
Short-term, at fair value, amortized cost (in dollars)	6,017	$ 6,807
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Fixed income securities, at fair value, amortized cost (in dollars)	286
Short-term, at fair value, amortized cost (in dollars)	61
Variable Interest Entity, Primary Beneficiary | Allstate Protection
Variable Interest Entity [Line Items]
Property and casualty insurance premiums	$ 45