Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net income	$ 50,613	$ 69,450	$ 102,018	$ 126,649
Other comprehensive income
Unrealized gain (loss) on foreign currency remeasurement	20,045	(21,321)	27,815	(15,343)
Realized and unrealized (loss) gain on derivative financial instruments	(8,196)	12,624	(12,121)	5,958
Other comprehensive income (loss)	11,849	(8,697)	15,694	(9,385)
Comprehensive income	62,462	60,753	117,712	117,264
Comprehensive income attributable to non-controlling interests		(6,369)		(6,521)
Comprehensive income attributable to Blackstone Mortgage Trust, Inc.	$ 62,462	$ 54,384	$ 117,712	$ 110,743