Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets	$ 737,741	$ 740,463
Liabilities	667,278	674,081
Consolidated Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	320	311
Liabilities	6	6
Investment Funds [Domain] | Consolidated Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	215	207
Liabilities	1	1
Renewable energy partnership | Consolidated Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	95	94
Liabilities	0	0
Other | Consolidated Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	10	10
Liabilities	$ 5	$ 5