Real Estate Assets - Real estate assets owned (Details)	Sep. 30, 2020 ft²	Sep. 30, 2020 number_of_properties	Sep. 30, 2020	Dec. 31, 2019 ft²	Sep. 30, 2019 ft²
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties | number_of_properties		125
Number of units in real estate property	680		12,936	12,256
Area of Real Estate Property	6,208,278			6,041,629
Area of Real Estate Property, Excluded from Floor Retail Space	3,169,000			3,204,000
Net Rentable Area	161,526				913,732
Lennox Portfolio
Business Combination Segment Allocation [Line Items]
Net Rentable Area	47,600
Armour And Brevard
Business Combination Segment Allocation [Line Items]
Net Rentable Area	35,000
Multifamily
Business Combination Segment Allocation [Line Items]
Number of units in real estate property | number_of_properties		1
Student housing
Business Combination Segment Allocation [Line Items]
Number of units in real estate property | number_of_properties		2
Shopping Center
Business Combination Segment Allocation [Line Items]
Number of units in real estate property | number_of_properties		2
Office Building
Business Combination Segment Allocation [Line Items]
Number of units in real estate property | number_of_properties		2
Lenox Portfolio [Member]
Business Combination Segment Allocation [Line Items]
Net Rentable Area	47,600
Lenox Portfolio [Member] | Construction in Progress
Business Combination Segment Allocation [Line Items]
Net Rentable Area	35,000
Office Building
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties			9	10
Multifamily
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties			44	42
Retail Site [Member]
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties			54	52
Student housing
Business Combination Segment Allocation [Line Items]
Number of beds, student housing			6,095	6,095