Consolidated Statements of Changes in Equity (USD $) In Thousands	Total	Class A Common Stock [Member]	Restricted Class A Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Blackstone Mortgage Trust Inc [Member]	Non-Controlling Interests [Member]
Balance at Dec. 31, 2012	$ 153,453	$ 293		$ 609,002		$ (535,851)	$ 73,444	$ 80,009
Reverse stock split	0	(263)		263			0
Shares of class A common stock issued	633,810	258		633,552			633,810
Deferred directors' compensation	75			75			75
Net (loss) income	5,170					(367)	(367)	5,537
Consolidation of subsidiary	11,962					5,727	5,727	6,235
Contributions from non-controlling interests	15,000						0	15,000
Purchase of and distributions to non-controlling interests	(17,803)						0	(17,803)
Balance at Jun. 30, 2013	801,667	288		1,242,892		(530,491)	712,689	88,978
Balance at Dec. 31, 2013	756,750	288	7	1,252,986	798	(536,170)	717,909	38,841
Shares of class A common stock issued	510,845	191		510,654			510,845
Restricted class A common stock earned	4,027		(2)	4,029			4,027
Dividends reinvested	0			97		(97)	0
Deferred directors' compensation	188			188			188
Other comprehensive income	1,930				1,930		1,930
Net (loss) income	51,555					46,531	46,531	5,024
Dividends declared on common stock	(42,122)					(42,122)	(42,122)
Distributions to non-controlling interests	(1,148)						0	(1,148)
Balance at Jun. 30, 2014	$ 1,282,025	$ 479	$ 5	$ 1,767,954	$ 2,728	$ (531,858)	$ 1,239,308	$ 42,717