Commitments, Contingencies and Guarantees (Commitments to Fund Investments) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Limited Partner [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 656	$ 685
Commercial Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	70	243
Bank Loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	141	181
Equity Release Mortgages [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 69	$ 87