REAL ESTATE HELD FOR INVESTMENT - Operating Leases, Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) tenant	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) tenant	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Operating Leased Assets [Line Items]
Recognition of deferred revenue, net of discontinued operations	$ 2,600	$ 3,200	$ 900	$ 1,000
Deferred rent receivables	16,700		16,700		$ 13,600
Incentive to lessee	$ 3,300		$ 3,300		3,100
Number of tenants | tenant	235		235
Adjustments to rental income	$ 400	$ 200	$ 1,100	$ 400
Prepaid expenses and other assets (Other liabilities)
Operating Leased Assets [Line Items]
Security deposit liability	$ 4,300		$ 4,300		$ 4,300
Maximum
Operating Leased Assets [Line Items]
Operating lease, term	12 years 10 months 24 days		12 years 10 months 24 days
Weighted Average
Operating Leased Assets [Line Items]
Operating lease, term	4 years 4 months 24 days		4 years 4 months 24 days
Apartment Building
Operating Leased Assets [Line Items]
Operating lease, term	1 year		1 year