Investments - Schedule of Details of Properties Acquired (Details) $ in Thousands		9 Months Ended
		Sep. 30, 2020 USD ($) Property	Jun. 30, 2020	Dec. 31, 2019 Property
Real Estate Properties [Line Items]
Ownership Interest			100.00%
Number of Properties		34		71
Real Estate Acquisition | $	[1]	$ 1,863,154
Multifamily
Real Estate Properties [Line Items]
Number of Properties		25		16
Office Buildings
Real Estate Properties [Line Items]
Number of Properties		2		12
Various | Southeast Affordable Housing Portfolio | Multifamily
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		21
Real Estate Acquisition | $	[1]	$ 574,253
Nashville, TN
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		6
Acquisition Date		Sep. 15, 2020
Real Estate Acquisition | $	[1]	$ 62,806
Nashville, TN | Nashville Office | Office Buildings
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Feb. 21, 2020
Real Estate Acquisition | $	[1]	$ 265,404
Chevy Chase, MD | Barlow Building | Medical Office
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Mar. 06, 2020
Real Estate Acquisition | $	[1]	$ 162,212
Boston, MA | 60 State St | Office Buildings
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Mar. 20, 2020
Real Estate Acquisition | $	[1]	$ 613,052
Columbus O H | Highlands Portfolio | Multifamily
Real Estate Properties [Line Items]
Ownership Interest		96.00%
Number of Properties		3
Acquisition Date		Jun. 23, 2020
Real Estate Acquisition | $	[1]	$ 103,228
Atlanta GA [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Aug. 21, 2020
Real Estate Acquisition | $	[1]	$ 82,199

[1] Purchase price is inclusive of acquisition-related costs.