SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Supplement Disclosures Related to Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounting Policies [Abstract]
Total interest costs incurred			$ 27,419	$ 26,730
Interest capitalized			911	747
Interest expense	$ 12,688	$ 12,652	26,508	25,983
Cash paid for interest, net of amounts capitalized			26,926	21,984
Cash paid for income taxes			337	296
Accounts payable and accrued liabilities for construction in progress			(1,192)	2,113
Accrued leasing commissions			1,040	498
Reduction to capital for prepaid offering costs			$ 236	$ 69