Secured Borrowings - Collateralized Loan Obligations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) Item	Dec. 31, 2020 USD ($) Item	May 31, 2021 USD ($)	Apr. 30, 2021 USD ($)	Aug. 31, 2019 USD ($)
Summary of CLO
Carrying value	$ 2,616,116	$ 930,554
Collateral assets
Summary of CLO
Amount issued	3,086,319
Carrying value	3,120,444
Financing
Summary of CLO
Amount issued	2,633,841
Carrying value	$ 2,616,116
STWD 2019-FL1
Summary of CLO
Amount issued					$ 1,100,000
STWD 2019-FL1 | Collateral assets
Summary of CLO
Count | Item	24	23
Amount issued	$ 1,092,887	$ 1,002,445
Carrying value	$ 1,103,513	$ 1,099,439
STWD 2019-FL1 | Financing
Summary of CLO
Count | Item	1	1
Amount issued	$ 936,375	$ 936,375
Carrying value	$ 933,049	$ 930,554
STWD 2019-FL1 | LIBOR | Collateral assets
Summary of CLO
Spread	4.19%	3.93%
STWD 2019-FL1 | LIBOR | Financing
Summary of CLO
Spread		1.64%
STWD 2019-FL1 | SOFR | Financing
Summary of CLO
Spread	1.63%
STWD 2021-FL2
Summary of CLO
Amount issued			$ 1,300,000
Percent of outstanding loan	7.00%
Debt, weighted average interest rate	7.49%
STWD 2021-FL2 | Collateral assets
Summary of CLO
Count | Item	25
Amount issued	$ 1,272,133
Carrying value	$ 1,279,678
STWD 2021-FL2 | Financing
Summary of CLO
Count | Item	1
Amount issued	$ 1,077,375
Carrying value	$ 1,069,691
STWD 2021-FL2 | LIBOR | Collateral assets
Summary of CLO
Spread	4.22%
STWD 2021-FL2 | LIBOR | Financing
Summary of CLO
Spread	1.78%
STWD 2021-SIF1
Summary of CLO
Amount issued				$ 500,000
Percent of outstanding loan	2.00%
Debt, weighted average interest rate	5.62%
STWD 2021-SIF1 | Collateral assets
Summary of CLO
Count | Item	31
Amount issued	$ 491,299
Carrying value	$ 506,666
STWD 2021-SIF1 | Financing
Summary of CLO
Count | Item	1
Amount issued	$ 410,000
Carrying value	$ 405,319
STWD 2021-SIF1 | LIBOR | Collateral assets
Summary of CLO
Spread	3.91%
STWD 2021-SIF1 | LIBOR | Financing
Summary of CLO
Spread	2.15%
STWD 2021-HTS | Collateral assets
Summary of CLO
Count | Item	1
Amount issued	$ 230,000
Carrying value	$ 230,587
STWD 2021-HTS | Financing
Summary of CLO
Count | Item	1
Amount issued	$ 210,091
Carrying value	$ 208,057
STWD 2021-HTS | LIBOR | Collateral assets
Summary of CLO
Spread	4.12%
STWD 2021-HTS | LIBOR | Financing
Summary of CLO
Spread	2.48%