Net Income (Loss) per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended										4 Months Ended	12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2009	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net Income (Loss) per Share
Net income (loss) attributable to Starwood Property Trust, Inc.	$ 41,028	$ 14,478	$ 32,424	$ 31,447	$ 17,573	$ 22,683	$ 10,849	$ 5,941	$ (1,098)	$ (1,919)	$ (3,017)	$ 119,377	$ 57,046	$ (3,017)
Net income (loss) allocated to participating securities												(2,226)	(1,388)	(97)
Numerator for basic and diluted net income (loss) per share												$ 117,151	$ 55,658	$ (3,114)
Basic weighted average shares outstanding (in shares)												84,974,604	49,138,720	47,575,634
Weighted average number of shares of diluted stock outstanding (in shares)												86,409,327	50,021,824	48,540,059
Basic income (loss) per share (in dollars per share)	$ 0.44	$ 0.15	$ 0.39	$ 0.43	$ 0.33	$ 0.47	$ 0.23	$ 0.12	$ (0.02)	$ (0.04)	$ (0.06)	$ 1.38	$ 1.16	$ (0.06)
Diluted income (loss) per share (in dollars per share)	$ 0.44	$ 0.15	$ 0.39	$ 0.43	$ 0.33	$ 0.47	$ 0.22	$ 0.12	$ (0.02)	$ (0.04)	$ (0.06)	$ 1.38	$ 1.14	$ (0.06)
Unvested restricted stock units (in shares)												998,604	1,690,810