Additional Information - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for reinsurance recoverables [Line Items]
Commitments to fund limited partnerships	$ 897
Retirement and employee savings plan expense	39	$ 37	$ 45
Allowance for reinsurance recoverables
Allowance for reinsurance recoverables [Line Items]
Aggregate allowance for losses on reinsurance recoverables	18	18
Net expense reduction against the allowance for losses on reinsurance recoverables		$ (2)
Reinsurance recoverable write-offs			2
Maximum | Allowance for reinsurance recoverables
Allowance for reinsurance recoverables [Line Items]
Net expense reduction against the allowance for losses on reinsurance recoverables	$ (1)		$ (1)