Real Estate - Real Estate Under Development and Construction in Progress - Additional Information (Details) $ in Thousands	3 Months Ended				12 Months Ended
	Jun. 30, 2021 USD ($) Property	Mar. 31, 2021 Property	Dec. 31, 2020 USD ($) Property	Mar. 31, 2020 Property	Dec. 31, 2020 USD ($)
Property, Plant and Equipment [Line Items]
Notes receivable, net	$ 117,280		$ 101,450		$ 101,450
Fund IV
Property, Plant and Equipment [Line Items]
Number of projects put into service during period | Property				1
Fund II
Property, Plant and Equipment [Line Items]
Notes receivable, net			33,800		33,800
Core Portfolio
Property, Plant and Equipment [Line Items]
Number of projects put into service during period | Property	1
Notes receivable, net	$ 16,000
Fund Portfolio
Property, Plant and Equipment [Line Items]
Notes receivable, net			$ 33,800		33,800
Fund Portfolio | Fund IV
Property, Plant and Equipment [Line Items]
Number of projects put into service during period | Property		1	2
Impairment charge			$ 16,500		$ 16,500
Cortlandt Crossing | Fund III
Property, Plant and Equipment [Line Items]
Number of projects put into service during period | Property				1