REDEEMABLE PREFERRED STOCK - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Class of Stock [Line Items]
Gross proceeds from issuance of preferred stock and warrants	$ 174,700,000
Net proceeds from issuance of preferred stock	15,484,000	$ 21,466,000
Issuance offering costs for preferred stock and warrants	14,600,000
Non-issuance offering costs for preferred stock and warrants	$ 7,900,000
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
Warrants outstanding (in shares)	4,603,287
Series A Preferred Stock
Class of Stock [Line Items]
Gross proceeds from issuance of preferred stock and warrants	$ 173,100,000
Issuance offering costs for preferred stock and warrants	14,400,000
Reclassification to deferred rent receivable and charges	$ 1,500,000
Preferred stock, shares outstanding (in shares)	7,098,258
Preferred stock, shares redeemed (in shares)	156,377
Series A Preferred Stock | Preferred Stock, Shares Issued, One
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	6,956,163
Series A Preferred Stock | Preferred Stock, Shares Issued, Two
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	298,472
Net proceeds from issuance of preferred stock	$ 0
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	31,025		19,145
Gross proceeds from issuance of preferred stock and warrants	$ 764,000
Net proceeds from issuance of preferred stock		$ 0
Issuance offering costs for preferred stock and warrants	27,000
Reclassification to deferred rent receivable and charges	$ 7,000
Preferred stock, shares outstanding (in shares)	31,025	0	19,145
Preferred stock, shares redeemed (in shares)	0
Series A Preferred Unit
Class of Stock [Line Items]
Number of securities called by warrants or rights (in shares)	1,194,159