Real Estate - Schedule of Acquisitions and Conversions (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Purchase Price	$ 95,750	$ 172,152
Fund V
Business Acquisition [Line Items]
Purchase Price	$ 95,750
Fund V | Canton Marketplace | GEORGIA
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 50,954
Fund V | Monroe Marketplace | PENNSYLVANIA
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price	$ 44,796
Core Portfolio
Business Acquisition [Line Items]
Purchase Price		158,143
Core Portfolio | Soho Acquisitions | 37 Greene Street - New York, NY
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price		15,689
Core Portfolio | 917 W. Armitage | 917 W. Armitage - Chicago, IL
Business Acquisition [Line Items]
Percent Acquired	100.00%
Purchase Price		3,515
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