Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Continuing Operations:
Basic - Income attributable to STWD common stockholders	$ 139,656	$ 127,016	$ 72,887	$ 197,399
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,143)	(751)	(2,365)	(1,575)
Basic earnings	138,513	126,265	70,522	195,824
Continuing Operations:
Basic - Income attributable to STWD common stockholders	139,656	127,016	72,887	197,399
Less: Income attributable to participating shares not already deducted as non-controlling interests	(1,143)	(751)	(2,365)	(1,575)
Add: Undistributed earnings to participating shares	120
Less: Undistributed earnings reallocated to participating shares	(116)
Diluted earnings	$ 141,568	$ 129,314	$ 70,522	$ 202,059
Number of Shares:
Basic - Average shares outstanding	281,461	279,239	281,225	278,396
Effect of dilutive securities - Convertible Notes (in shares)	9,649	9,649		9,963
Effect of dilutive securities - Unvested non-participating shares	183	184	215	170
Diluted - Average shares outstanding	291,293	289,072	281,440	288,529
Basic:
Basic (in dollars per share)	$ 0.49	$ 0.45	$ 0.25	$ 0.70
Diluted:
Diluted (in dollars per share)	$ 0.49	$ 0.45	$ 0.25	$ 0.70
Convertible Senior Notes
Continuing Operations:
Add: Interest expense on Convertible Notes	$ 3,051	$ 3,049		$ 6,235