Loans Portfolio - Schedule of Carrying Value of The Loans Receivable And Interests In Loans Receivable (Details) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($) Loan	Dec. 31, 2020 USD ($) Loan
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	99	98
Principal Balance	$ 6,602,804	$ 6,491,288
Carrying Value	6,502,145	$ 6,464,095
Carrying value gross	6,569,169
Allowance for loan losses	$ (67,024)
Risk Rating One
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	1	3
Principal Balance	$ 35,721	$ 68,372
Carrying Value	$ 35,699	$ 69,418
Risk Rating Two
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	7	6
Principal Balance	$ 705,886	$ 349,159
Carrying Value	$ 703,714	$ 349,342
Risk Rating Three
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	74	72
Principal Balance	$ 4,678,785	$ 4,691,775
Carrying Value	$ 4,649,076	$ 4,668,991
Risk Rating Four
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	15	16
Principal Balance	$ 1,155,879	$ 1,366,982
Carrying Value	$ 1,154,147	$ 1,367,344
Risk Rating Five
Financing Receivable Allowance For Credit Losses [Line Items]
Number of Loans \| Loan	2	1
Principal Balance	$ 26,533	$ 15,000
Carrying Value	$ 26,533	$ 9,000

Mortgage loans on real estate commercial and consumer.

No definition available.

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Namespace Prefix:	cmtg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of contractual principal due at origination of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column F
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column F))
-URI http://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

+ Details

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Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of mortgage loans within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 3
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 3))
-URI http://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

+ Details

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Namespace Prefix:	srt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123605502&loc=d3e21338-158488

+ Details

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

- 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

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

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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- Details

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