FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit, fair value	$ 77,600	$ 81,600
Mortgage loans payable	123,470	126,601
Note to affiliate	4,000	4,500
RREEF America
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note to affiliate	4,000	4,500
Mortgages
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans payable	123,470	126,601
Wells Fargo Bank
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit, fair value	$ 77,600	$ 81,600