FAIR VALUE DISCLOSURES - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	$ 53,985	$ 59,832
Preferred equity investments	26,186	44,493
Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,176,155	1,328,714
Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	94,383	$ 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	1,176,155
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	53,985
Preferred equity investments	26,186
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	94,383
Measured on a Recurring Basis | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	53,985
Preferred equity investments	26,186
Measured on a Recurring Basis | Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,176,155
Measured on a Recurring Basis | Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 94,383