Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Continuing Operations:
Basic - Income attributable to STWD common stockholders	$ 88,428	$ 105,766	$ 308,166	$ 243,896
Less: Income attributable to participating shares	(761)	(456)	(2,489)	(1,743)
Basic earnings	87,667	105,310	305,677	242,153
Continuing Operations:
Basic - Income attributable to STWD common stockholders	88,428	105,766	308,166	243,896
Less: Income attributable to participating shares	(761)	(456)	(2,489)	(1,743)
Diluted earnings	$ 87,667	$ 105,310	$ 305,677	$ 242,153
Number of Shares:
Basic - Average shares outstanding	259,759	237,429	259,412	237,017
Effect of dilutive securities - Convertible Notes (in shares)	2,313	3,445	2,284	3,766
Effect of dilutive securities - Contingently Issuable Shares (in shares)	236	138	236	138
Effect of dilutive securities — Unvested non-participating shares	129	79	123	61
Diluted - Average shares outstanding	262,437	241,091	262,055	240,982
Basic:
Basic (in dollars per share)	$ 0.34	$ 0.44	$ 1.18	$ 1.02
Diluted:
Diluted (in dollars per share)	$ 0.33	$ 0.44	$ 1.17	$ 1.00