Earnings per Share - Reconciliation of Net Income and Number of Shares used in Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Basic Earnings
Income attributable to STWD common stockholders	$ 47,435	$ 194,562	$ 268,252	$ 731,448
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,510)	(2,929)	(4,962)	(15,673)
Basic earnings	45,925	191,633	263,290	715,775
Diluted Earnings
Income attributable to STWD common stockholders	47,435	194,562	268,252	731,448
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,510)	(2,929)	(4,962)	(15,673)
Add: Undistributed earnings to participating shares	0	1,818	0	11,629
Less: Undistributed earnings reallocated to participating shares	0	(1,763)	0	(11,280)
Diluted earnings	$ 45,925	$ 194,594	$ 263,290	$ 724,848
Number of Shares:
Basic - Average shares outstanding (in shares)	310,268	306,704	309,471	304,908
Effect of dilutive securities - Contingently issuable shares (in shares)	0	23	0	23
Effect of dilutive securities - Unvested non-participating shares (in shares)	298	199	267	161
Diluted - Average shares outstanding (in shares)	310,566	316,575	309,738	314,741
Earnings Per Share Attributable to STWD Common Stockholders:
Basic (in dollars per share)	$ 0.15	$ 0.62	$ 0.85	$ 2.35
Diluted (in dollars per share)	$ 0.15	$ 0.61	$ 0.85	$ 2.30
Unamortized discount—Convertible Notes
Diluted Earnings
Add: Interest expense on Convertible Notes		$ 2,906		$ 8,724
Number of Shares:
Effect of dilutive securities - Convertible Notes (in shares)		9,649		9,649