Investments (Leased Real Estate Investments - Operating Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	$ 4,893	$ 4,132
Office
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	1,999	1,999
Operating Lease, Lease Income	175	169	$ 157
Retail
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	1,127	1,006
Operating Lease, Lease Income	102	95	92
Apartment
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	778	253
Operating Lease, Lease Income	24	70	72
Industrial
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	306	223
Operating Lease, Lease Income	46	38	39
Land
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	514	489
Operating Lease, Lease Income	21	19	13
Hotel
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	93	94
Operating Lease, Lease Income	7	3	2
Other
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, carrying value	76	68
Operating Lease, Lease Income	5	5	4
Leased real estate investments
Schedule of Operating Leases by Property Type [Line Items]
Operating Lease, Lease Income	$ 380	$ 399	$ 379