ACQUISITIONS AND DISPOSITIONS - Disposals (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) ft²	Mar. 31, 2018 USD ($)
Disposal Group
Ownership sold, percentage	100.00%
Disposed Property Information
Sales Price	$ 652,891	$ 0
Gain on sale of real estate	377,581	$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposed Property Information
Sales Price	694,566
Transaction Costs	13,948
Gain on sale of real estate	$ 377,581
March Oakland Properties, Oakland, CA \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposed Property Information
Square Feet \| ft²	975,596
Sales Price	$ 512,016
Transaction Costs	8,971
Gain on sale of real estate	$ 289,779
830 1st Street, Washington, D.C. \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposed Property Information
Square Feet \| ft²	247,337
Sales Price	$ 116,550
Transaction Costs	2,438
Gain on sale of real estate	$ 45,710
260 Townsend Street, San Francisco, CA \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposed Property Information
Square Feet \| ft²	66,682
Sales Price	$ 66,000
Transaction Costs	2,539
Gain on sale of real estate	$ 42,092

Disposal Group, Including Discontinued Operation, Sales Transaction Costs

No definition available.

Name:	cmct_DisposalGroupIncludingDiscontinuedOperationSalesTransactionCosts
Namespace Prefix:	cmct_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of ownership sold during the period.

+ References

No definition available.

+ Details

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

- Definition

The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(9)(a))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(7)(c))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(14)(d))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(a))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

+ Details

Name:	us-gaap_GainsLossesOnSalesOfInvestmentRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Net rentable area for properties owned.

+ References

No definition available.

+ Details

Name:	us-gaap_NetRentableArea
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfRealEstateHeldforinvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=cmct_MarchOaklandPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=cmct_A8301stStreetWashingtonD.C.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=cmct_A260TownsendStreetSanFranciscoCAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: