Real Estate - Schedule of Acquisitions and Conversions (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Purchase Price	$ 172,152	$ 324,339
Core Portfolio
Business Acquisition [Line Items]
Purchase Price	$ 158,143	$ 146,435
Core Portfolio | 849 and 912 W. Armitage - Chicago, IL
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 10,738
Core Portfolio | 917 W. Armitage - Chicago, IL
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 3,515
Core Portfolio | 8436-8452 Melrose Place - Los Angeles, CA
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 48,691
Core Portfolio | Soho Acquisitions | 37 Greene Street - New York, NY
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 15,689
Core Portfolio | Soho Acquisitions | 41,45, 47, 51 and 53 Greene Street - New York, NY
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 87,006
Core Portfolio | Town Center | Wilmington, DE
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 138,939
Fund IV
Business Acquisition [Line Items]
Purchase Price	$ 14,009
Fund IV | 230-240 W. Broughton Street | GEORGIA
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 13,219
Fund IV | 102 E. Broughton Street | GEORGIA
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 790
Fund V
Business Acquisition [Line Items]
Purchase Price		$ 177,904
Fund V | Palm Coast Landing | Palm Coast, FL
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 36,644
Fund V | Lincoln Commons | Lincoln, RI
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 54,299
Fund V | Landstown Commons | Virginia Beach, VA
Business Acquisition [Line Items]
Percent Acquired		100.00%
Purchase Price		$ 86,961