Secured Financing Agreements (Details) (USD $)	12 Months Ended					12 Months Ended				12 Months Ended			12 Months Ended			12 Months Ended				12 Months Ended			12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Fourth Wells Repurchase Agreement	Dec. 31, 2011 TIAA Portfolio	Dec. 31, 2011 Starwood Property Mortgage Sub-1, L.L.C. Wells Repurchase Agreement	Dec. 31, 2011 Starwood Property Mortgage Sub-2, L.L.C. Second Wells Repurchase Agreement option Y	Dec. 31, 2011 Starwood Property Mortgage Sub-2, L.L.C. Second Wells Repurchase Agreement Minimum	Dec. 31, 2011 Starwood Property Mortgage Sub-2, L.L.C. Second Wells Repurchase Agreement Maximum	Dec. 31, 2011 Starwood Property Mortgage Sub-3, L.L.C. Goldman Repurchase Agreement	Dec. 31, 2011 Starwood Property Mortgage Sub-3, L.L.C. Goldman Repurchase Agreement Minimum	Dec. 31, 2011 Starwood Property Mortgage Sub-3, L.L.C. Goldman Repurchase Agreement Maximum	Dec. 31, 2011 Starwood Property Mortgage, L.L.C. Wells RMBS Repurchase Agreement	Dec. 31, 2011 Starwood Property Mortgage, L.L.C. Wells RMBS Repurchase Agreement Minimum	Dec. 31, 2011 Starwood Property Mortgage, L.L.C. Wells RMBS Repurchase Agreement Maximum	Dec. 31, 2011 Starwood Property Mortgage Sub-6, L.L.C. Fourth Wells Repurchase Agreement unit Y option M	Dec. 31, 2011 Starwood Property Mortgage Sub-4, L.L.C. Deutsche Repurchase Agreement option Y	Jun. 30, 2011 Starwood Property Mortgage Sub-4, L.L.C. Deutsche Repurchase Agreement Minimum	Jun. 30, 2011 Starwood Property Mortgage Sub-4, L.L.C. Deutsche Repurchase Agreement Maximum	Dec. 31, 2011 SPT Rosslyn Holdings, L.L.C. Second Deutsche Repurchase Agreement	Dec. 31, 2011 SPT Rosslyn Holdings, L.L.C. Second Deutsche Repurchase Agreement Minimum	Dec. 31, 2011 SPT Rosslyn Holdings, L.L.C. Second Deutsche Repurchase Agreement Maximum	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement M	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement LIBOR	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement LIBOR Minimum	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement LIBOR Maximum	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement Base rate	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement Base rate Minimum	Dec. 31, 2011 SPT Real Estate Sub II, LLC BAML Credit agreement Base rate Maximum
Debt Instrument:
Loan portfolio collateralized						$ 162,300,000
Asset purchase capacity				144,300,000		108,900,000	550,000,000			150,000,000			100,000,000			236,000,000	150,000,000			117,400,000
Increase in asset purchase capacity							200,000,000
Pricing rate, basis						one-month LIBOR	one-month LIBOR			one-month LIBOR			one-month LIBOR			one-month LIBOR	one-month LIBOR			one-month LIBOR				LIBOR			base rate
Pricing margin (as a percent)						3.00%		1.75%	6.00%		1.95%	2.25%		1.50%	1.75%	2.75%		1.85%	2.50%		3.50%	5.00%			2.35%	2.50%		1.35%	1.50%
Additional pricing margin in event of default (as a percent)						4.00%	4.00%			2.00%			4.00%				4.00%			5.00%			2.00%
Debt outstanding	1,103,517,000	579,659,000		35,300,000		108,900,000	435,300,000			92,100,000			86,600,000			144,300,000				117,300,000			119,000,000
Carrying value of collateral						162,300,000	630,800,000			128,600,000			136,800,000			307,400,000				164,700,000			176,800,000
Maximum liability guaranteed (as a percent)						25.00%		25.00%	100.00%	25.00%							25.00%
Maximum liability guaranteed																	20,000,000
Number of extension options (in options)							2									2	2
Extended term							1									1	1						12
Number of properties collateralizing loans originated or acquired																26
Acquisitions/Origination	1,782,964,000	1,352,253,000	215,048,000													307,300,000
Maturity period (in years)																3
Borrowings outstanding, due in June 2012																32,500,000
Extended term subject to borrowings outstanding due in June 2012																6
Extension fee percentage																0.25%
Commitment fee (as a percent)																0.50%
Extension fee percentage for each year if the overall facility is extended beginning in December 2014																0.25%
Guaranteed liability subject to currently outstanding repurchase price for all purchased assets (as a percent)																60.00%
Guaranteed liability subject to outstanding balance of any individual repurchase transaction (as a percent)																100.00%
Operating cash flows as percentage of collateral loan receivable for which the company guarantees 100% of the outstanding repurchase price, maximum																15.00%
Amount of loan under credit agreement																							119,000,000
Repayment of secured financings
2012	398,905,000				59,700,000			2,300,000															5,600,000
2013	491,135,000
2014	213,477,000
Total	$ 1,103,517,000