FAIR VALUE DISCLOSURES - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	$ 56,956	$ 59,832
Preferred equity investments	43,039	44,493
Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,311,354	1,328,714
Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	79,249	$ 105,510
Measured on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	0
Preferred equity investments	0
Measured on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Measured on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Measured on a Recurring Basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	0
Preferred equity investments	0
Measured on a Recurring Basis | Significant Other Observable Inputs (Level 2) | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,311,354
Measured on a Recurring Basis | Significant Other Observable Inputs (Level 2) | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	56,956
Preferred equity investments	43,039
Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3) | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3) | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	79,249
Measured on a Recurring Basis | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	56,956
Preferred equity investments	43,039
Measured on a Recurring Basis | Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,311,354
Measured on a Recurring Basis | Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 79,249