BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Lease incentives	$ 4,000,000.0	$ 4,000,000.0
Lease incentives, accumulated amortization	2,400,000	2,000,000.0
Allowance for uncollectible accounts receivable	1,900,000	45,000
Tenant recoveries outside of lease agreements	0	$ 205,000	$ 399,000
Performance obligations	$ 0