FAIR VALUE DISCLOSURES - Face Values, Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, face value	$ 96,492,000	$ 91,280,000
Preferred equity investments, face value	43,851,000	48,035,000
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, face value	1,300,000,000	1,300,000,000
Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, face value	117,464,000	259,202,000
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	69,460,000	65,907,000
Preferred equity investments	44,262,000	48,483,000
Carrying Amount | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,307,394,000	1,306,286,000
Carrying Amount | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	115,679,000	256,430,000
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	65,797,000	65,892,000
Preferred equity investments	43,825,000	47,064,000
Fair Value | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,270,877,000	1,329,191,000
Fair Value | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 101,820,000	$ 246,461,000