FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Financial Instruments Not Recorded at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Carrying Amount
Liabilities:
Mortgages payable	$ 414,851	$ 414,760
Junior subordinated notes	25,173	25,133
Carrying Amount \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	40,777	0
Carrying Amount \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	20,883	21,728
Carrying Amount \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	9,946	58,904
Carrying Amount \| Commercial mortgage loans receivable
Assets:
Loans receivable	0	424
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring \| Level 3
Liabilities:
Mortgages payable	402,736	413,819
Junior subordinated notes	24,335	24,162
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring \| Level 3 \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	41,558	0
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring \| Level 3 \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	21,279	22,157
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring \| Level 3 \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	10,572	61,277
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring \| Level 3 \| Commercial mortgage loans receivable
Assets:
Loans receivable	$ 0	$ 424

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611

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- Definition

Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- References

No definition available.

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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