Stockholders' Equity (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income (Loss) from Continuing Operations per Share of Common Stock
(Loss) income from continuing operations	$ (1,597)	$ 141,195
Net (income) loss attributable to noncontrolling interests	(1,518)	(74,069)
(Loss) income from continuing operations attributable to Blackstone Mortgage Trust, Inc.	$ (3,115)	$ 67,126
Weighted average shares outstanding, basic	3,016,425	2,283,741
Warrants and options outstanding for the purchase of class A common stock		146,406
Weighted average shares outstanding, diluted	3,016,425	2,430,147
Per share amount, basic	$ (1.03)	$ 29.39
Per share amount, diluted	$ (1.03)	$ 27.64