REAL ESTATE - Additional Information (Details) $ in Thousands, ft² in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) ft² numberOfProperties	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft² numberOfProperties	Jun. 30, 2019 USD ($)
Real Estate Properties [Line Items]
Rentable square feet | ft²	7.8		7.8
Percentage of portfolio occupied	88.00%		88.00%
Impairment charges on real estate | $	$ 0	$ 0	$ 19,896	$ 8,706
Office Properties
Real Estate Properties [Line Items]
Number of real estate properties	18		18
Mixed-use Office/Retail Property
Real Estate Properties [Line Items]
Number of real estate properties	1		1
Held for Investment | Office Properties
Real Estate Properties [Line Items]
Number of real estate properties	18		18