Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Continuing Operations:
Basic - Income (loss) attributable to STWD common stockholders	$ 111,378	$ (66,769)
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,925)	(1,222)
Basic earnings (loss)	109,453	(67,991)
Continuing Operations:
Basic - Income (loss) attributable to STWD common stockholders	111,378	(66,769)
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,925)	(1,222)
Add: Loss on extinguishment of Convertible Notes	(516)	(170)
Diluted earnings (loss)	$ 112,369	$ (67,991)
Number of Shares:
Basic - Average shares outstanding	283,319	280,990
Effect of dilutive securities - Contingently issuable shares (in shares)	263
Diluted - Average shares outstanding	293,231	280,990
Basic:
Basic (in dollars per share)	$ 0.39	$ (0.24)
Diluted:
Diluted (in dollars per share)	$ 0.38	$ (0.24)
Convertible Senior Notes
Continuing Operations:
Add: Interest expense on Convertible Notes	$ 2,916
Number of Shares:
Effect of dilutive securities - Convertible Notes (in shares)	9,649