FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Financial Instruments Not Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Carrying Amount
Liabilities:
Mortgages payable	$ 97,100	$ 97,100
Junior subordinated notes	27,070	27,070
Carrying Amount \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	42,839	32,509
Carrying Amount \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	20,172	23,606
Carrying Amount \| SBA 7(a) loans receivable, paycheck protection program
Assets:
Loans receivable	7,364	14,089
Carrying Amount \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	8,099	8,822
Carrying Amount \| SBA 7(a) loans receivable, held for sale
Assets:
Loans receivable	16,342	4,109
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3
Liabilities:
Junior subordinated notes	24,327	24,236
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	42,906	32,397
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	21,693	24,850
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, paycheck protection program
Assets:
Loans receivable	7,622	14,484
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	8,186	8,914
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, held for sale
Assets:
Loans receivable	17,950	4,527
Fair Value, Measurements, Nonrecurring \| Estimated Fair Value \| Fair Value, Inputs, Level 1 And Level 2
Liabilities:
Mortgages payable	$ 101,094	$ 100,799

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

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

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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.

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