REDEEMABLE PREFERRED STOCK - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Gross proceeds from issuance of preferred stock and warrants	$ 157,700,000
Net proceeds from issuance of Preferred Stock	41,958,000	$ 37,197,000	$ 35,984,000
Issuance offering costs for preferred stock and warrants	13,000,000.0
Non-issuance offering costs for preferred stock and warrants	$ 7,300,000
Series A Preferred Warrants
Class of Stock [Line Items]
Warrants issued (in shares)	4,603,287
Gross proceeds from issuance of preferred stock and warrants	$ 761,000
Issuance offering costs for preferred stock and warrants	142,000
Reclassification to deferred rent receivable and charges	5,000
Series A Preferred Stock
Class of Stock [Line Items]
Gross proceeds from issuance of preferred stock and warrants	156,500,000
Issuance offering costs for preferred stock and warrants	12,800,000
Reclassification to deferred rent receivable and charges	$ 1,300,000
Preferred stock, shares outstanding (in shares)	6,385,618
Preferred stock, shares redeemed (in shares)	107,014
Series A Preferred Stock | Preferred Stock, Shares Issued, One
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	6,290,900
Series A Preferred Stock | Preferred Stock, Shares Issued, Two
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	201,732
Net proceeds from issuance of Preferred Stock	$ 0
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	19,145	0
Gross proceeds from issuance of preferred stock and warrants	$ 473,000
Issuance offering costs for preferred stock and warrants	14,000
Reclassification to deferred rent receivable and charges	$ 4,000
Preferred stock, shares outstanding (in shares)	19,145	0	0
Preferred stock, shares redeemed (in shares)	0
Series A Preferred Unit
Class of Stock [Line Items]
Outstanding common stock available for purchase (in shares)	1,194,159