Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net income (loss)	$ 18,505	$ 75,551	$ (34,780)	$ 152,418
Other comprehensive income
Unrealized gain (loss) on foreign currency translation	21,342	(9,578)	(48,166)	(4,164)
Realized and unrealized (loss) gain on derivative financial instruments	(30,665)	10,914	73,325	8,966
Other comprehensive (loss) income	(9,323)	1,336	25,159	4,802
Comprehensive income (loss)	9,182	76,887	(9,621)	157,220
Comprehensive income attributable to non-controlling interests	(961)	(377)	(1,028)	(680)
Comprehensive income (loss) attributable to Blackstone Mortgage Trust, Inc.	$ 8,221	$ 76,510	$ (10,649)	$ 156,540