Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Continuing Operations:
Basic - Income attributable to STWD common stockholders	$ 127,016	$ 109,230	$ 197,399	$ 209,162
Less: Income attributable to participating shares not already deducted as non-controlling interests	(751)	(1,034)	(1,575)	(1,755)
Basic earnings	126,265	108,196	195,824	207,407
Continuing Operations:
Basic - Income attributable to STWD common stockholders	127,016	109,230	197,399	209,162
Less: Income attributable to participating shares not already deducted as non-controlling interests	(751)	(1,034)	(1,575)	(1,755)
Diluted earnings	$ 129,314	$ 115,789	$ 202,059	$ 222,566
Number of Shares:
Basic - Average shares outstanding	279,239	260,998	278,396	260,832
Effect of dilutive securities - Convertible Notes (in shares)	9,649	27,134	9,963	27,044
Effect of dilutive securities - Contingently issuable shares (in shares)		128		128
Effect of dilutive securities - Unvested non-participating shares	184	50	170	36
Diluted - Average shares outstanding	289,072	288,310	288,529	288,040
Basic:
Basic (in dollars per share)	$ 0.45	$ 0.41	$ 0.70	$ 0.80
Diluted:
Diluted (in dollars per share)	$ 0.45	$ 0.40	$ 0.70	$ 0.77
Convertible Senior Notes
Continuing Operations:
Add: Interest expense on Convertible Notes	$ 3,049	$ 7,593	$ 6,235	$ 15,159