Investment Securities - SEREF (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2012	Dec. 31, 2019
Residential Real Estate
Fair value of the investment	$ 45,336		$ 26,746
Ownership percentage	2.00%
SEREF
Residential Real Estate
Number of shares acquired		9,140,000
Fair value of the investment	$ 11,200		$ 12,700

Represents the number of shares acquired in the equity security investment.

No definition available.

Name:	stwd_InvestmentInEquitySecuritiesNumberOfSharesAcquired
Namespace Prefix:	stwd_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage ownership in the equity security investment.

+ References

No definition available.

+ Details

Name:	stwd_InvestmentInEquitySecuritiesPercentageOwnership
Namespace Prefix:	stwd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714

+ Details

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=stwd_StarwoodEuropeanRealEstateFinanceLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: