Borrowing base period for eligible pledged assets become ineligible.

No definition available.

Name:	ck0001690012_BorrowingBasePeriodForEligiblePledgedAssetsBecomeIneligible
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Convertible by option term loan initial maturity period.

+ References

No definition available.

+ Details

Name:	ck0001690012_ConvertibleByOptionTermLoanInitialMaturityPeriod
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument floor rate.

+ References

No definition available.

+ Details

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

- Definition

Debt instrument loan-to-appraised value percentage.

+ References

No definition available.

+ Details

Name:	ck0001690012_DebtInstrumentLoanToAppraisedValuePercentage
Namespace Prefix:	ck0001690012_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument loan-to-unpaid balance percentage.

+ References

No definition available.

+ Details

Name:	ck0001690012_DebtInstrumentLoanToUnpaidBalancePercentage
Namespace Prefix:	ck0001690012_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Increased interest rate due to failure to meet the minimum deposit balance.

+ References

No definition available.

+ Details

Name:	ck0001690012_IncreasedInterestRateDueToFailureToMeetTheMinimumDepositBalance
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

Minimum required average unrestricted aggregate deposit account balance amount to be maintained.

+ References

No definition available.

+ Details

Name:	ck0001690012_MinimumRequiredAverageUnrestrictedAggregateDepositAccountBalanceAmountToBeMaintained
Namespace Prefix:	ck0001690012_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Percentage of conversion fee of convertible by option term loan.

+ References

No definition available.

+ Details

Name:	ck0001690012_PercentageOfConversionFeeOfConvertibleByOptionTermLoan
Namespace Prefix:	ck0001690012_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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_AtlasRepoFacilityMember
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:	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_LineOfCreditFacilityAxis=ck0001690012_JPMorganRepoFacilityMember
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_WesternAllianceCreditFacilityMember
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, Credit Facility and Mortgage Loan Payable - Additional Information (Details) - USD ($)				1 Months Ended		3 Months Ended		9 Months Ended	32 Months Ended
	May 05, 2023	Mar. 09, 2023	Mar. 10, 2021	Nov. 30, 2023	May 31, 2022	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2025	Dec. 31, 2021	Dec. 31, 2024	May 06, 2019
Repurchase Agreement [Line Items]
Carrying value of the mortgage loan payable								$ 23,804,000		$ 0
Atlas Repo Facility
Repurchase Agreement [Line Items]
Repurchase agreement, maximum advance amount				$ 100,000,000
Maturity date				Nov. 08, 2024
Atlas Repo Facility \| Secured Overnight Financing Rate (SOFR) \| Minimum
Repurchase Agreement [Line Items]
Interest rate spread								2.50%
Floor rate								0.15%
Atlas Repo Facility \| Secured Overnight Financing Rate (SOFR) \| Maximum
Repurchase Agreement [Line Items]
Interest rate spread								3.00%
Floor rate								0.25%
JP Morgan Repo Facility
Repurchase Agreement [Line Items]
Repurchase agreement, maximum advance amount	$ 526,076,000										$ 150,000,000
Maturity date	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								2.00%
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								2.85%
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%
Western Alliance Credit Facility
Repurchase Agreement [Line Items]
Repurchase agreement, maximum advance amount		$ 40,000,000	$ 75,000,000
Interest rate spread		3.50%
Floor rate		2.50%
Maturity date		Mar. 10, 2025	Mar. 10, 2023
Borrowing base period for eligible pledged assets become ineligible			36 months
Convertible by option term loan initial maturity period			2 years
Percentage of conversion fee of convertible by option term loan.			0.25%
Minimum required average unrestricted aggregate deposit account balance amount to be maintained						$ 5,000,000	$ 3,750,000
Increased interest rate due to failure to meet the minimum deposit balance			0.50%
Western Alliance Credit Facility \| Minimum
Repurchase Agreement [Line Items]
Loan-to-unpaid balance percentage			60.00%
Loan-to-appraised value percentage			45.00%
Western Alliance Credit Facility \| Maximum
Repurchase Agreement [Line Items]
Loan-to-unpaid balance percentage			70.00%
Loan-to-appraised value percentage			50.00%
Western Alliance Credit Facility \| London Interbank Offered Rate
Repurchase Agreement [Line Items]
Interest rate spread			3.25%
Floor rate			0.75%
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								$ 23,804,000
Ladder Capital Finance LLC \| Secured Overnight Financing Rate (SOFR)
Repurchase Agreement [Line Items]
Interest rate spread								2.95%