Debt instrument floor rate.

No definition available.

Name:	ck0001690012_DebtInstrumentFloorRate
Namespace Prefix:	ck0001690012_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility Option To Extend Maturity Date.

+ References

No definition available.

+ Details

Name:	ck0001690012_LineOfCreditFacilityOptionToExtendMaturityDate
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility option to extend maturity description.

+ References

No definition available.

+ Details

Name:	ck0001690012_LineOfCreditFacilityOptionToExtendMaturityDescription
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Mortgage loan maturity date.

+ References

No definition available.

+ Details

Name:	ck0001690012_MortgageLoanMaturityDate
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Mortgage Loans Outstanding Amount

+ References

No definition available.

+ Details

Name:	ck0001690012_MortgageLoansOutstandingAmount
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Mortgage loans payable, net.

+ References

No definition available.

+ Details

Name:	ck0001690012_MortgageLoansPayableNet
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Repurchase agreement line items.

+ References

No definition available.

+ Details

Name:	ck0001690012_RepurchaseAgreementLineItems
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

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

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=ck0001690012_JPMorganRepoFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=ck0001690012_LondonInterbankOfferedRatesLiborMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=ck0001690012_LadderCapitalFinanceLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Repurchase Agreements and Mortgage Loan Payable - Additional Information (Details) - USD ($)			1 Months Ended	3 Months Ended	9 Months Ended	32 Months Ended
	May 05, 2026	May 05, 2023	May 31, 2022	Mar. 31, 2026	Sep. 30, 2025	Dec. 31, 2021	Dec. 31, 2025	May 06, 2019
Repurchase Agreement [Line Items]
Carrying value of the mortgage loan payable				$ 23,978,000			$ 23,891,000
JP Morgan Repo Facility
Repurchase Agreement [Line Items]
Repurchase agreement, maximum advance amount		$ 526,076,000						$ 150,000,000
Maturity date	May 06, 2027	May 06, 2026	May 06, 2023
Option to extend maturity date		May 06, 2028
Option to extend maturity, description					two optional one-year extensions
JP Morgan Repo Facility \| Minimum
Repurchase Agreement [Line Items]
Interest rate spread				0.00%
JP Morgan Repo Facility \| Maximum
Repurchase Agreement [Line Items]
Interest rate spread				3.00%
JP Morgan Repo Facility \| Secured Overnight Financing Rate (SOFR) \| Minimum
Repurchase Agreement [Line Items]
Interest rate spread				1.85%
JP Morgan Repo Facility \| Secured Overnight Financing Rate (SOFR) \| Maximum
Repurchase Agreement [Line Items]
Interest rate spread				2.50%
JP Morgan Repo Facility \| London Interbank Offered Rate \| Minimum
Repurchase Agreement [Line Items]
Interest rate spread						1.75%
JP Morgan Repo Facility \| London Interbank Offered Rate \| Maximum
Repurchase Agreement [Line Items]
Interest rate spread						2.50%
Ladder Capital Finance LLC
Repurchase Agreement [Line Items]
Floor rate					6.20%
Aggregate principal amount outstanding					$ 24,500,000
Mortgage loan outstanding				$ 24,500,000
Mortgage loan maturity date					Oct. 06, 2027
Carrying value of the mortgage loan payable				$ 23,978,000
Ladder Capital Finance LLC \| Secured Overnight Financing Rate (SOFR)
Repurchase Agreement [Line Items]
Interest rate spread					2.95%