Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
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_DividendsPayableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash outflow to owners or shareholders, excluding ordinary dividends. Includes special dividends.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

+ Details

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

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=cmct_CommonStockExcludingPrivateRepurchaseParticipantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands										6 Months Ended
	Jun. 04, 2018	Mar. 06, 2018	Jan. 11, 2018	Dec. 18, 2017	Jun. 27, 2017	Jun. 12, 2017	Apr. 24, 2017	Apr. 05, 2017	Mar. 08, 2017	Jun. 30, 2018	Jun. 30, 2017
Dividends Payable [Line Items]
Payment of special cash dividends										$ 1,575	$ 4,872
Common Stock
Dividends Payable [Line Items]
Dividends per common share (in usd per share)	$ 0.125	$ 0.125				$ 0.125			$ 0.21875
Common Stock, Excluding Private Repurchase Participants
Dividends Payable [Line Items]
Dividends per common share (in usd per share)				$ 0.73		$ 1.98		$ 0.28
Payment of special cash dividends			$ 1,575		$ 4,271		$ 601