BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Rent Receivable and Charges (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Deferred rent receivable	$ 54,798	$ 52,619
Deferred leasing costs	49,460	52,414
Deferred leasing costs, accumulated amortization	22,557	23,807
Deferred offering costs	4,185	3,401
Other deferred costs	$ 276	$ 121