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.

No definition available.

+ Details

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

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_EUR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PositionAxis=us-gaap_LongMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PositionAxis=us-gaap_ShortMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_GBP
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_AUD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=stwd_InterestRateSwapPayingFixedRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_USD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=stwd_InterestRateSwapReceivingFixedRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CreditIndexProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=stwd_InterestRateSwapGuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivatives and Hedging Activity - Designated and Non-Designated Hedges (Details) € in Thousands, £ in Thousands, $ in Thousands, $ in Thousands	Sep. 30, 2021 EUR (€) contract	Sep. 30, 2021 GBP (£) contract	Sep. 30, 2021 AUD ($) contract	Sep. 30, 2021 USD ($) contract
Derivatives
Number of Contracts	418	418	418	418
Foreign exchange contracts \| EUR \| Long
Derivatives
Number of Contracts	17	17	17	17
Aggregate Notional Amount \| €	€ 52,389
Foreign exchange contracts \| EUR \| Short
Derivatives
Number of Contracts	131	131	131	131
Aggregate Notional Amount \| €	€ 255,128
Foreign exchange contracts \| GBP \| Long
Derivatives
Number of Contracts	13	13	13	13
Aggregate Notional Amount \| £		£ 9,935
Foreign exchange contracts \| GBP \| Short
Derivatives
Number of Contracts	131	131	131	131
Aggregate Notional Amount \| £		£ 534,811
Foreign exchange contracts \| AUD \| Short
Derivatives
Number of Contracts	51	51	51	51
Aggregate Notional Amount \| $			$ 259,803
Interest rate swaps – Paying fixed rates \| USD
Derivatives
Number of Contracts	44	44	44	44
Aggregate Notional Amount \| $				$ 2,469,098
Interest rate swaps – Receiving fixed rates \| USD
Derivatives
Number of Contracts	2	2	2	2
Aggregate Notional Amount \| $				$ 473,200
Interest rate caps \| GBP
Derivatives
Number of Contracts	1	1	1	1
Aggregate Notional Amount \| £		£ 61,000
Interest rate caps \| USD
Derivatives
Number of Contracts	20	20	20	20
Aggregate Notional Amount \| $				$ 939,893
Credit index instruments \| USD
Derivatives
Number of Contracts	3	3	3	3
Aggregate Notional Amount \| $				$ 49,000
Interest rate swap guarantees \| USD
Derivatives
Number of Contracts	5	5	5	5
Aggregate Notional Amount \| $				$ 309,443