FAIR VALUE DISCLOSURES - Summary of Face Values, Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, Face Value	$ 129,341	$ 53,484
Preferred equity investment, Face Value	51,833	44,882
Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, Face Value	1,300,000	700,000
Mortgage indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, Face Value	260,371	163,638
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	97,478	50,846
Preferred equity investments	52,288	45,190
Carrying Amount [Member] | Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,305,996	688,246
Carrying Amount [Member] | Mortgage indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	257,571	160,752
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	97,722	51,914
Preferred equity investments	52,926	48,332
Fair Value [Member] | Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,341,106	709,500
Fair Value [Member] | Mortgage indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 248,041	$ 150,091