Secured Borrowings - Narrative (Details)	1 Months Ended				3 Months Ended
	Mar. 31, 2022 USD ($)	Feb. 28, 2022 USD ($)	Jan. 31, 2022 USD ($)	Jul. 31, 2021 USD ($) hotel	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	May 31, 2021 USD ($)	Apr. 30, 2021 USD ($)	Aug. 31, 2019 USD ($)
Secured Borrowings
Principal amount of notes purchased by third-party investors				$ 210,100,000
RMBS
Secured Borrowings
Securitizations of loans				$ 230,000,000
Number of hotels | hotel				41
Residential Loan Credit Facility
Secured Borrowings
Maximum borrowing capacity	$ 500,000,000	$ 250,000,000			$ 500,000,000
Initial maturity extension	18 months
Extension term	3 years
STWD 2022-FL3
Secured Borrowings
Amount issued		1,000,000,000
Principal amount of notes purchased by third-party investors		842,500,000
Long term debt, gross		82,500,000
Liquidation preference		$ 75,000,000
CLO contribution period		2 years
STWD 2021-FL2
Secured Borrowings
Amount issued								$ 1,300,000,000
Principal amount of notes purchased by third-party investors								1,100,000,000
Long term debt, gross								70,100,000
Liquidation preference								$ 127,500,000
Additional contribution to CLO					87,000,000
STWD 2019-FL1
Secured Borrowings
Amount issued										$ 1,100,000,000
Principal amount of notes purchased by third-party investors										936,400,000
Long term debt, gross										86,600,000
Liquidation preference										$ 77,000,000
Repayments of debt					71,100,000
STWD 2021-SIF2
Secured Borrowings
Amount issued			$ 500,000,000
Principal amount of notes purchased by third-party investors			410,000,000
Liquidation preference			$ 90,000,000
CLO contribution period			3 years
Additional contribution to CLO					63,100,000
STWD 2021-SIF1
Secured Borrowings
Amount issued									$ 500,000,000
Principal amount of notes purchased by third-party investors									410,000,000
Liquidation preference									$ 90,000,000
Additional contribution to CLO					25,200,000
CLOs and SASB
Secured Borrowings
Amortization of deferred financing costs					2,400,000	$ 600,000
Incurred debt issuance costs					37,800,000
Deferred financing costs, net of amortization	$ 26,200,000				26,200,000		$ 17,700,000
JPMorgan Chase Bank N.A.
Secured Borrowings
Amount at risk	666,800,000				$ 666,800,000
Weighted average extended maturities					3 years 6 months
Morgan Stanley Bank, N.A.
Secured Borrowings
Amount at risk	$ 659,800,000				$ 659,800,000
Weighted average extended maturities					3 years 7 months 6 days
Repurchase Agreements
Secured Borrowings
Percentage of repurchase agreements for which margin calls are limited to collateral specific credit marks	66.00%				66.00%
Percentage of repurchase agreements containing margin call provisions for general capital market activity	34.00%				34.00%
Percentage of repurchase agreements containing margin call provisions that pertain to loans held-for-sale	12.00%				12.00%
Secured Borrowings
Secured Borrowings
Amortization of deferred financing costs					$ 9,600,000	$ 9,500,000
Long term debt, gross	$ 11,604,153,000				$ 11,604,153,000		$ 12,654,420,000