Represents the consecutive trading period as a basis for debt conversion.

No definition available.

Name:	stwd_DebtInstrumentConsecutiveTradingPeriodAsABasisForDebtConversion
Namespace Prefix:	stwd_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of convertible debt's if-converted value.

+ References

No definition available.

+ Details

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

- Definition

The amount by which the convertible debt's if-converted value is less than its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

+ References

No definition available.

+ Details

Name:	stwd_DebtInstrumentConvertibleIfConvertedValueLessThanPrincipal
Namespace Prefix:	stwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the minimum number of conditions to be satisfied for conversion of debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	stwd_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum trading period as a basis for debt conversion.

+ References

No definition available.

+ Details

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Namespace Prefix:	stwd_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of conversion price and last reported sales price as a basis for debt conversion.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of conversion price as a basis for debt conversion.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of per share value of distributions that exceeds the market price of the entity's common stock as a basis for debt conversion.

+ References

No definition available.

+ Details

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

- Definition

Represents the period of average closing market price of common stock as a basis for debt conversion.

+ References

No definition available.

+ Details

Name:	stwd_DebtInstrumentPeriodOfAverageClosingMarketPriceAsBasisForDebtConversion
Namespace Prefix:	stwd_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

+ References

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

- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

No definition available.

+ Details

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

- Definition

The price per share of the conversion feature embedded in the debt instrument.

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

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

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	stwd_ConditionsForDebtConversionAxis=stwd_SalePriceConditionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	stwd_ConditionsForDebtConversionAxis=stwd_TradingPriceConditionMember
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_DebtInstrumentAxis=stwd_SeniorNotesDue2026Member
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodTwoMember
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Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stwd_ConvertibleSeniorNotesDue2023Member
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- Details

Name:	us-gaap_DebtInstrumentAxis=stwd_ConvertibleSeniorNotesDue2017Member
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Unsecured Senior Notes - Narrative (Details) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Item $ / shares	Sep. 30, 2020 USD ($)	Jul. 14, 2021 USD ($)	Mar. 29, 2017 USD ($)
Unsecured Senior Notes
Interest expense	$ 115,531	$ 95,981	$ 328,558	$ 317,499
Closing share price (in dollars per share) \| $ / shares	$ 24.41		$ 24.41
Minimum \| Conversion upon satisfaction of closing market price condition
Unsecured Senior Notes
Period of average closing market price of common stock as a basis for debt conversion			10 days
Convertible Senior Notes
Unsecured Senior Notes
Interest expense	$ 2,900	$ 3,100	$ 8,700	$ 9,200
Minimum number of conditions to be satisfied for conversion of debt \| Item			1
Convertible Senior Notes \| Conversion upon satisfaction of closing market price condition
Unsecured Senior Notes
Minimum trading period as a basis for debt conversion			20 days
Consecutive trading period as a basis for debt conversion			30 days
Convertible Senior Notes \| Conversion upon satisfaction of trading price condition
Unsecured Senior Notes
Consecutive trading period as a basis for debt conversion			5 days
Convertible Senior Notes \| Minimum \| Conversion upon satisfaction of closing market price condition
Unsecured Senior Notes
Percentage of per share value of distributions that exceeds the market price of the entity's common stock as a basis for debt conversion			10.00%
Convertible Senior Notes \| Maximum \| Conversion upon satisfaction of trading price condition
Unsecured Senior Notes
Percentage of conversion price and last reported sales price as a basis for debt conversion			98.00%
2026 Senior Notes
Unsecured Senior Notes
Amount issued					$ 400,000
Coupon Rate	3.63%		3.63%		3.625%
2026 Senior Notes \| Prior to January 15, 2026
Unsecured Senior Notes
Redemption percentage			100.00%
2026 Senior Notes \| On and after January 15, 2026
Unsecured Senior Notes
Redemption percentage			100.00%
2026 Senior Notes \| Prior to July 15, 2023
Unsecured Senior Notes
Redemption percentage			40.00%
2023 Convertible Notes
Unsecured Senior Notes
Amount issued						$ 250,000
Coupon Rate	4.38%		4.38%			4.375%
Amount by which if-converted value of the Notes are less than principal amount			$ 14,500
Conversion price (in dollars per share) \| $ / shares	$ 25.91		$ 25.91
If-converted value	$ 235,500		$ 235,500
Convertible notes carrying value	249,000		249,000
Convertible notes fair value	$ 255,600		$ 255,600
2017 Notes \| Convertible Notes and Senior Notes \| Minimum \| Conversion upon satisfaction of closing market price condition
Unsecured Senior Notes
Percentage of conversion price as a basis for debt conversion			110.00%