FAIR VALUE DISCLOSURES - Inputs Used for Valuation of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	$ 65,797	$ 65,892
Preferred equity investments	43,825	47,064
Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,270,877	1,329,191
Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	101,820	$ 246,461
Recurring | 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
Recurring | 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
Recurring | 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
Recurring | 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
Recurring | Significant Other Observable Inputs (Level 2) | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,270,877
Recurring | Significant Other Observable Inputs (Level 2) | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	65,797
Preferred equity investments	43,825
Recurring | Significant Unobservable Inputs (Level 3) | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	0
Recurring | Significant Unobservable Inputs (Level 3) | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	101,820
Recurring | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	65,797
Preferred equity investments	43,825
Recurring | Total | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,270,877
Recurring | Total | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 101,820