Investments (Leased Real Estate Investments - Operating Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	$ 5,450	$ 4,893
Office
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	2,351	1,999
Operating Lease, Lease Income	188	175	$ 169
Retail
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	1,147	1,127
Operating Lease, Lease Income	93	102	95
Apartment
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	810	778
Operating Lease, Lease Income	62	24	70
Land
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	621	514
Operating Lease, Lease Income	25	21	19
Industrial
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	332	306
Operating Lease, Lease Income	56	46	38
Hotel
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	96	93
Operating Lease, Lease Income	5	7	3
Other
Schedule of Operating Leases by Property Type [Line Items]
Leased real estate investments, Carrying Value	93	76
Operating Lease, Lease Income	6	5	5
Leased real estate investments
Schedule of Operating Leases by Property Type [Line Items]
Operating Lease, Lease Income	$ 435	$ 380	$ 399