Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net (loss) income	$ (53,283)	$ 76,867
Other comprehensive income
Unrealized (loss) gain on foreign currency translation	(69,510)	5,414
Realized and unrealized gain (loss) on derivative financial instruments	103,991	(1,948)
Other comprehensive income	34,481	3,466
Comprehensive (loss) income	(18,802)	80,333
Comprehensive income attributable to non-controlling interests	(67)	(302)
Comprehensive (loss) income attributable to Blackstone Mortgage Trust, Inc.	$ (18,869)	$ 80,031