Loan Securitization/Sale Activities - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commercial and Residential Lending Segment
Loan Transfer Activities
Net gains (losses) on the sale of loan qualifying for sales treatment	$ 0	$ (300,000)	$ 0	$ (100,000)
Infrastructure Lending Segment
Loan Transfer Activities
Loans held-for-sale face amount	$ 0	$ 0	$ 0	$ 0

Net gain or loss resulting from the difference between the sale price and the carrying value when a financial asset transferred in a securitization, asset-backed financing arrangement, or similar transfer is accounted for as a sale, including those transactions in which the seller or transferor has continuing involvement with the financial assets that have been transferred.

No definition available.

Name:	stwd_AmountOfNetGainOrLossFromSaleOfFinancialAssetsInSecuritizations
Namespace Prefix:	stwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration