Real Estate Assets Real estate assets owned (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) ft²	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2019	Dec. 31, 2019 number_of_properties
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties		19	19	123
Number of units in real estate property	477	1,347
New Market Properties [Member]
Business Combination Segment Allocation [Line Items]
business combination purchase price | $	$ 92.4	$ 197.0
Area of Real Estate Property	1,318,519	674,981
Office Building [Member]
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties		7	10
Net Rentable Area	626,000	1,226,000
Area of Real Estate Property, Excluded from Floor Retail Space	3,204,000	2,578,000
Multifamily [Member]
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties		32	34
Number of units in real estate property		9,768	10,245
Retail Site [Member]
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties		45	52
Area of Real Estate Property	6,041,629	4,730,695
student housing [Member]
Business Combination Segment Allocation [Line Items]
Number of Real Estate Properties		7	8
Number of units in real estate property		1,679	2,011
Number of beds, student housing		5,208	6,095
Lenox Portfolio [Member]
Business Combination Segment Allocation [Line Items]
Net Rentable Area	47,600