BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Rent Receivable and Charges (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Deferred Rent Receivable and Charges
Deferred rent receivable	$ 61,990,000	$ 58,612,000
Deferred leasing costs, gross	65,689,000	59,225,000
Deferred leasing costs, accumulated amortization	25,008,000	20,612,000
Deferred offering costs	$ 1,868,000	$ 0