BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Consolidated Statements of Operations
Asset management and other fees to related parties	$ 2,259	$ 2,645
Consolidated Statements of Cash Flows
Depreciation and amortization, net	5,017	5,102
Deferred rent and amortization of intangible assets, liabilities and lease inducements		0
Other assets	(2,530)	(1,355)
Payment of unsecured revolving lines of credit, revolving credit facilities, mortgages payable, term notes and principal on SBA 7(a) loan-backed notes	(7,653)	(9,249)
Payment of principal on SBA 7(a) loan-backed notes		0
Net proceeds from issuance of Preferred Stock	5,465	8,643
Preferred stock offering costs offset against redeemable preferred stock	87	178
Preferred stock offering costs offset against redeemable preferred stock in permanent equity		0
Series D Preferred Stock
Consolidated Statements of Cash Flows
Net proceeds from issuance of Preferred Stock		0
Non-segment
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment	605	812
Operating Segments
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment	$ 731	682
As previously reported
Consolidated Statements of Operations
Asset management and other fees to related parties		4,139
Consolidated Statements of Cash Flows
Depreciation and amortization, net		5,258
Deferred rent and amortization of intangible assets, liabilities and lease inducements		(816)
Other assets		(695)
Payment of unsecured revolving lines of credit, revolving credit facilities, mortgages payable, term notes and principal on SBA 7(a) loan-backed notes		(5,000)
Payment of principal on SBA 7(a) loan-backed notes		(4,249)
Net proceeds from issuance of Preferred Stock		8,497
Preferred stock offering costs offset against redeemable preferred stock		176
Preferred stock offering costs offset against redeemable preferred stock in permanent equity		2
As previously reported | Series D Preferred Stock
Consolidated Statements of Cash Flows
Net proceeds from issuance of Preferred Stock		146
As previously reported | Non-segment
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment		0
As previously reported | Operating Segments
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment		0
Reclassification
Consolidated Statements of Operations
Asset management and other fees to related parties		(1,494)
Consolidated Statements of Cash Flows
Depreciation and amortization, net		(156)
Deferred rent and amortization of intangible assets, liabilities and lease inducements		816
Other assets		(660)
Payment of unsecured revolving lines of credit, revolving credit facilities, mortgages payable, term notes and principal on SBA 7(a) loan-backed notes		(4,249)
Payment of principal on SBA 7(a) loan-backed notes		4,249
Net proceeds from issuance of Preferred Stock		146
Preferred stock offering costs offset against redeemable preferred stock		2
Preferred stock offering costs offset against redeemable preferred stock in permanent equity		(2)
Reclassification | Series D Preferred Stock
Consolidated Statements of Cash Flows
Net proceeds from issuance of Preferred Stock		(146)
Reclassification | Non-segment
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment		812
Reclassification | Operating Segments
Consolidated Statements of Operations
Expense reimbursements to related parties—lending segment		$ 682