Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Continuing Operations:
Basic - Income attributable to STWD common stockholders									$ 365,186	$ 450,697	$ 496,572
Less: Income attributable to participating shares									(2,053)	(3,434)	(5,579)
Basic earnings									363,133	447,263	490,993
Discontinued Operations:
Loss from discontinued operations											(1,551)
Basic - Net income attributable to STWD common stockholders after allocation to participating shares									363,133	447,263	489,442
Continuing Operations:
Basic - Income attributable to STWD common stockholders									365,186	450,697	496,572
Less: Income attributable to participating shares									(2,053)	(3,434)	(5,579)
Add: Undistributed earnings to participating shares											918
Less: Undistributed earnings reallocated to participating shares											(902)
Diluted earnings									363,133	447,263	491,009
Discontinued Operations:
Basic - Loss from discontinued operations											(1,551)
Diluted - Net income attributable to STWD common stockholders after allocation to participating shares									$ 363,133	$ 447,263	$ 489,458
Number of Shares:
Basic - Average shares outstanding									238,529	233,419	214,945
Effect of dilutive securities - Convertible Notes (in shares)									2,697	97	3,432
Effect of dilutive securities - Contingently Issuable Shares (in shares)									473	524	404
Effect of dilutive securities — Unvested non-participating shares									95	102
Diluted - Average shares outstanding									241,794	234,142	218,781
Basic:
Income from continuing operations (in dollars per share)									$ 1.52	$ 1.92	$ 2.29
Loss from discontinued operations (in dollars per share)											(0.01)
Basic (in dollars per share)	$ 0.50	$ 0.44	$ 0.47	$ 0.11	$ 0.40	$ 0.49	$ 0.49	$ 0.53	1.52	1.92	2.28
Diluted:
Income from continuing operations (in dollars per share)									1.50	1.91	2.25
Loss from discontinued operations (in dollars per share)											(0.01)
Diluted (in dollars per share)	$ 0.49	$ 0.44	$ 0.47	$ 0.11	$ 0.40	$ 0.49	$ 0.49	$ 0.52	$ 1.50	$ 1.91	$ 2.24
Net Income (Loss) Attributable to Parent	$ 121,290	$ 105,766	$ 111,473	$ 26,657	$ 96,451	$ 116,735	$ 117,148	$ 120,363	$ 365,186	$ 450,697	$ 495,021