FAIR VALUE DISCLOSURES - Face Values, Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, face value	$ 67,527,000	$ 96,492,000
Preferred equity investments, face value	43,893,000	43,851,000
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, face value	1,250,000,000	1,300,000,000
Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, face value	114,777,000	117,464,000
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	63,070,000	69,460,000
Preferred equity investments	44,304,000	44,262,000
Carrying Amount | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,248,773,000	1,307,394,000
Carrying Amount | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	113,070,000	115,679,000
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable	59,832,000	65,797,000
Preferred equity investments	44,493,000	43,825,000
Fair Value | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	1,328,714,000	1,270,877,000
Fair Value | Secured Indebtedness
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities	$ 105,510,000	$ 101,820,000