FAIR VALUE OF FINANCIAL INSTRUMENTS - Unobservable Inputs (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
SBA 7(a) loans receivable, subject to loan-backed notes \| Minimum
Liabilities:
Rate of prepayment	9.59%
SBA 7(a) loans receivable, subject to loan-backed notes \| Maximum
Liabilities:
Rate of prepayment	17.50%
Loans Receivable and Commercial Mortgage Loans \| Minimum
Liabilities:
Rate of prepayment	4.91%	7.30%
Loans Receivable and Commercial Mortgage Loans \| Maximum
Liabilities:
Rate of prepayment	17.50%	17.50%
SBA 7(a) loans receivable, subject to secured borrowings \| Minimum
Liabilities:
Rate of prepayment	10.29%	15.50%
SBA 7(a) loans receivable, subject to secured borrowings \| Maximum
Liabilities:
Rate of prepayment	17.50%	17.50%
Carrying Amount
Liabilities:
Mortgages payable	$ 386,923	$ 414,760
Junior subordinated notes	25,215	25,133
Carrying Amount \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	37,031	0
Carrying Amount \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	29,748	58,904
Carrying Amount \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	16,469	21,728
Carrying Amount \| Commercial mortgage loans receivable
Assets:
Loans receivable	0	424
Estimated Fair Value \| Level 3
Liabilities:
Mortgages payable	377,364	413,819
Junior subordinated notes	24,462	24,162
Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to loan-backed notes
Assets:
Loans receivable	38,357	0
Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to credit risk
Assets:
Loans receivable	30,630	61,277
Estimated Fair Value \| Level 3 \| SBA 7(a) loans receivable, subject to secured borrowings
Assets:
Loans receivable	16,706	22,157
Estimated Fair Value \| Level 3 \| Commercial mortgage loans receivable
Assets:
Loans receivable	$ 0	$ 424
Measurement Input, Discount Rate \| SBA 7(a) loans receivable, subject to loan-backed notes \| Minimum
Liabilities:
Measurement input for loans receivable	0.0675
Measurement Input, Discount Rate \| SBA 7(a) loans receivable, subject to loan-backed notes \| Maximum
Liabilities:
Measurement input for loans receivable	0.0925
Measurement Input, Discount Rate \| Loans Receivable and Commercial Mortgage Loans \| Minimum
Liabilities:
Measurement input for loans receivable	0.0675	0.0625
Measurement Input, Discount Rate \| Loans Receivable and Commercial Mortgage Loans \| Maximum
Liabilities:
Measurement input for loans receivable	0.0975	0.0900
Measurement Input, Discount Rate \| SBA 7(a) loans receivable, subject to secured borrowings \| Minimum
Liabilities:
Measurement input for loans receivable	0.0875
Measurement Input, Discount Rate \| SBA 7(a) loans receivable, subject to secured borrowings \| Maximum
Liabilities:
Measurement input for loans receivable	0.0950
Measurement Input, Discount Rate \| Mortgages payable \| Minimum
Liabilities:
Measurement input for debt	0.0462	0.0415
Measurement Input, Discount Rate \| Mortgages payable \| Maximum
Liabilities:
Measurement input for debt	0.0464	0.0428
Measurement Input, Discount Rate \| Junior subordinated notes
Liabilities:
Measurement input for debt	0.0705	0.0594

Financing Receivable, Measurement Input

No definition available.

Name:	cmct_FinancingReceivableMeasurementInput
Namespace Prefix:	cmct_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the prepayment interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	cmct_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Value of input used to measure long-term debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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Namespace Prefix:
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