BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Lease incentives	$ 4,000,000		$ 4,000,000		$ 4,000,000
Lease incentives, accumulated amortization	2,600,000		2,600,000		2,400,000
Allowance for uncollectible accounts receivable	1,700,000		1,700,000		$ 1,900,000
Tenant recoveries outside of lease agreements	0	$ 0	0	$ 0
Remaining performance obligations	$ 0		$ 0