Loans (Details) (USD $)	9 Months Ended	12 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Investments in mortgages and loans
Carrying Value	$ 1,987,587,000	$ 1,425,243,000
Face Amount	2,077,006,000	1,525,605,000
Loans with variable rates of interest	797,600,000	332,700,000
Loans with variable rates of interest (as a percent)	40.10%	23.30%
Weighted average spread of loans (as a percent)	4.73%	2.30%
Variable rate basis of loans	LIBOR, 1-Month LIBOR, 3-Month LIBOR	LIBOR, 1-Month LIBOR, 3-Month LIBOR
Risk ratings by class of loan
Total loans	1,987,587,000	1,425,243,000
Movement of loans held for investment
Beginning Balance	1,425,243,000
Acquisitions/Origination	1,243,740,000
Additional fundings (l)	44,807,000
Capitalized Interest	4,404,000
Loans sold	(288,812,000)
Loan maturities	(264,615,000)
Transfer out - loan converted to a security	(176,635,000)
Principal repayments	(13,092,000)
Discount/premium amortization	18,461,000
Unrealized foreign currency remeasurement loss	(4,189,000)
Unrealized loss on loans held for sale at fair value	(1,725,000)
Balance at the end of the period	1,987,587,000	1,425,243,000
Total loans held for investment
Investments in mortgages and loans
Carrying Value	1,816,047,000	1,230,783,000
Face Amount	1,903,392,000	1,330,966,000
Risk ratings by class of loan
Total loans	1,816,047,000	1,230,783,000
First Mortgages
Investments in mortgages and loans
Carrying Value	765,198,000	757,684,000
Face Amount	781,829,000	797,154,000
Weighted Average Coupon (as a percent)	7.80%	6.90%
Weighted Average Life (years)	3.3	3.3
Risk ratings by class of loan
Total loans	765,198,000	757,684,000
First Mortgages \| Rating 2
Investments in mortgages and loans
Carrying Value	88,436,000
Risk ratings by class of loan
Total loans	88,436,000
First Mortgages \| Rating 3
Investments in mortgages and loans
Carrying Value	642,689,000
Risk ratings by class of loan
Total loans	642,689,000
First Mortgages \| Rating 4
Investments in mortgages and loans
Carrying Value	34,073,000
Risk ratings by class of loan
Total loans	34,073,000
Subordinated Mortgages
Investments in mortgages and loans
Carrying Value	415,636,000	406,410,000
Face Amount	468,215,000	465,929,000
Weighted Average Coupon (as a percent)	6.70%	6.60%
Weighted Average Life (years)	4.2	4.9
Risk ratings by class of loan
Total loans	415,636,000	406,410,000
Subordinated Mortgages \| Rating 2
Investments in mortgages and loans
Carrying Value	129,831,000
Risk ratings by class of loan
Total loans	129,831,000
Subordinated Mortgages \| Rating 3
Investments in mortgages and loans
Carrying Value	232,202,000
Risk ratings by class of loan
Total loans	232,202,000
Subordinated Mortgages \| Rating 4
Investments in mortgages and loans
Carrying Value	53,603,000
Risk ratings by class of loan
Total loans	53,603,000
Mezzanine Loans
Investments in mortgages and loans
Carrying Value	635,213,000	66,689,000
Face Amount	653,348,000	67,883,000
Weighted Average Coupon (as a percent)	8.50%	10.80%
Weighted Average Life (years)	3.2	4.8
Risk ratings by class of loan
Total loans	635,213,000	66,689,000
Mezzanine Loans \| Rating 2
Investments in mortgages and loans
Carrying Value	138,294,000
Risk ratings by class of loan
Total loans	138,294,000
Mezzanine Loans \| Rating 3
Investments in mortgages and loans
Carrying Value	489,253,000
Risk ratings by class of loan
Total loans	489,253,000
Mezzanine Loans \| Rating 4
Investments in mortgages and loans
Carrying Value	7,666,000
Risk ratings by class of loan
Total loans	7,666,000
First mortgages held for sale at fair value
Investments in mortgages and loans
Carrying Value	121,229,000	144,163,000
Face Amount	122,954,000	143,901,000
Weighted Average Coupon (as a percent)	5.90%	5.70%
Weighted Average Life (years)	9.2	4.9
Risk ratings by class of loan
Total loans	121,229,000	144,163,000
First mortgages held for sale at fair value \| Rating 2
Investments in mortgages and loans
Carrying Value	84,295,000
Risk ratings by class of loan
Total loans	84,295,000
First mortgages held for sale at fair value \| Rating 3
Investments in mortgages and loans
Carrying Value	36,934,000
Risk ratings by class of loan
Total loans	36,934,000
Loans held in securitization trust
Investments in mortgages and loans
Carrying Value	50,311,000	50,297,000
Face Amount	50,660,000	50,738,000
Weighted Average Coupon (as a percent)	5.00%	5.00%
Weighted Average Life (years)	3.7	4.2
Risk ratings by class of loan
Total loans	50,311,000	50,297,000
Loans held in securitization trust \| Rating 2
Investments in mortgages and loans
Carrying Value	13,214,000
Risk ratings by class of loan
Total loans	13,214,000
Loans held in securitization trust \| Rating 3
Investments in mortgages and loans
Carrying Value	37,097,000
Risk ratings by class of loan
Total loans	37,097,000
Rating 1
Investments in mortgages and loans
Maximum LTV (as a percent)	65.00%
Rating 2
Investments in mortgages and loans
Carrying Value	454,070,000
Maximum LTV (as a percent)	70.00%
Risk ratings by class of loan
Total loans	454,070,000
Rating 3
Investments in mortgages and loans
Carrying Value	1,438,175,000
Maximum LTV (as a percent)	80.00%
Risk ratings by class of loan
Total loans	1,438,175,000
Rating 4
Investments in mortgages and loans
Carrying Value	95,342,000
LTV, low end of range (as a percent)	80.00%
LTV, high end of range (as a percent)	90.00%
Risk ratings by class of loan
Total loans	95,342,000
Rating 5
Investments in mortgages and loans
Threshold LTV (as a percent)	90.00%
California
Investments in mortgages and loans
Face Amount	165,500,000
Risk ratings by class of loan
Number of units in the portfolio	6
Northern Virginia
Investments in mortgages and loans
Face Amount	188,000,000
Risk ratings by class of loan
Interest acquired in mezzanine loan (as a percent)	90.00%
Number of units in the portfolio	10
Amount of mortgage collateralized	156,500,000
U.S
Investments in mortgages and loans
Face Amount	137,800,000
Risk ratings by class of loan
Number of units in the portfolio	28
Amount of mortgage collateralized	127,100,000
North Carolina
Investments in mortgages and loans
Face Amount	175,000,000
Pennsylvania
Investments in mortgages and loans
Face Amount	60,500,000
Risk ratings by class of loan
Number of units in the portfolio	2
1-month LIBOR
Investments in mortgages and loans
Loans with variable rates of interest	670,300,000	211,500,000
Weighted average spread of loans (as a percent)	0.2394%	0.2606%
3-month LIBOR
Investments in mortgages and loans
Loans with variable rates of interest	$ 127,300,000	$ 121,200,000
Weighted average spread of loans (as a percent)	0.3743%	0.3028%

Represents the high end of the range of loan to value ratio that is used to classify a loan into a particular credit rating category.

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Represents the low end of the range of loan to value ratio that is used to classify a loan into a particular credit rating category.

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- Definition

Represents the maximum loan to value ratio that is one of the criteria for classifying a loan into a particular credit rating category.

+ Details

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Data Type:	num:percentItemType
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- Definition

Represents the interest acquired in mortgage loan on real estate.

+ Details

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Namespace Prefix:	stwd
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Total amount of interest capitalized on mortgage loans on real estate during the reporting period.

+ Details

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Namespace Prefix:	stwd
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The collateralized amount of real estate mortgage loans.

+ Details

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Balance Type:	debit
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- Definition

The proceeds from the principal collected on maturity of loans collateralized by real estate during the reporting period.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The amount of mortgage loans on real estate transferred out during the reporting period.

+ Details

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Balance Type:	credit
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- Definition

Represents the unrealized foreign currency measurement gain or loss on mortgage loans.

+ Details

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Balance Type:	debit
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- Definition

Represents the unrealized gain or loss during the period due to fair value measurement of mortgage loans.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the duration of the mortgage loan receivable or the weighted average duration on a group of loans.

+ Details

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Namespace Prefix:	stwd
Data Type:	xbrli:decimalItemType
Balance Type:	na
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- Definition

Reflects the carrying amount of mortgage loans charging borrowers variable or adjustable rates of interest.

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- Definition

Reflects the percentage of mortgage loans charging borrowers variable or adjustable rates of interest.

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Data Type:	num:percentItemType
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- Definition

Represents the loan to value ratio above which a loan is classified into a particular credit rating category.

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- Definition

The percentage points (also referred to as 'margin') added to the reference rate as stated in the loan agreement and used to compute the variable rate on the loans receivable. For instance, the loan agreement might state that the interest rate the borrower is obligated to pay is the London Interbank Offered Rate (LIBOR) plus three quarters (3/4) of a percentage point adjusted quarterly (each three months). LIBOR in this example is the index or reference rate, 3/4 percentage point is the margin, the reference rate plus the margin is the fully indexed rate. This element would be used to report separately the margin.

+ Details

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Data Type:	num:percentItemType
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- Definition

The reference rate for the variable rate of the loans receivable, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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- Definition

Total carrying amount of mortgage loans as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29.6)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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-Publisher SEC

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-Number 210

-Section 04

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

-Number 210

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Subparagraph (SX 210.5-04.(c) Schedule IV)

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Balance Type:	debit
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Data Type:	xbrli:stringItemType
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- Definition

The amount of premium on mortgage loans on real estate amortized during the reporting period.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

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-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

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Name:	us-gaap_MortgageLoansOnRealEstateCarryingAmountOfMortgages
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of principal collected on mortgage loans on real estate during the reporting period.

+ References

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCollectionsOfPrincipal
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying amount of mortgage loans on real estate that were sold during the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the contractual principal due at the origination of the mortgage loan (face amount).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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-Publisher SEC

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-Number 210

-Section 04

-Paragraph c

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-Article 5

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-Publisher SEC

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-Number 210

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

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-Publisher SEC

-Name Regulation S-X (SX)

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-Paragraph c

-Subparagraph Schedule IV

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

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Data Type:	num:percentItemType
Balance Type:	na
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- 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.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

Total amount of new mortgage loans on real estate during the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Total amount of additions to mortgage loans other than new loans during the reporting period.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ Details

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