Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2026 USD ($)
Loan Funding Commitments \| Commercial and Residential Lending Segment
Property, Plant and Equipment [Line Items]
Value of loans with future funding commitments	$ 2,300.0
Value of loans with future funding commitments expected to fund	1,900.0
Loan Funding Commitments \| Infrastructure Lending Segment
Property, Plant and Equipment [Line Items]
Value of loans with future funding commitments	441.9
Revolvers and Letters of Credit \| Infrastructure Lending Segment
Property, Plant and Equipment [Line Items]
Value of loans with future funding commitments	278.9
Delayed Draw Term Loans \| Infrastructure Lending Segment
Property, Plant and Equipment [Line Items]
Value of loans with future funding commitments	163.0
Loan Purchase Commitments \| Infrastructure Lending Segment
Property, Plant and Equipment [Line Items]
Outstanding loan purchase commitment	149.0
Construction Funding Commitments \| Property Segment
Property, Plant and Equipment [Line Items]
Value of loans with future funding commitments	$ 67.9

Represents the value of loans with future funding commitments.

No definition available.

Name:	stwd_LoansWithFutureFundingCommitmentsValue
Namespace Prefix:	stwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the value of loans with future funding commitments expected to fund.

+ References

No definition available.

+ Details

Name:	stwd_LoansWithFutureFundingCommitmentsValueExpectedToFund
Namespace Prefix:	stwd_
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

+ Details

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

- Definition

Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(17))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-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(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=stwd_LoanFundingCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=stwd_CommercialAndResidentialLendingSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=stwd_InfrastructureLendingSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=stwd_RevolversAndLettersOfCreditCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=stwd_DelayedDrawTermLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_LoanPurchaseCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=stwd_ConstructionFundingCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=stwd_PropertySegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: