Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net income (loss)	$ 80,540	$ (53,283)
Other comprehensive income
Unrealized loss on foreign currency translation	(34,957)	(69,510)
Realized and unrealized gain on derivative financial instruments	35,071	103,991
Other comprehensive income	114	34,481
Comprehensive income (loss)	80,654	(18,802)
Comprehensive income attributable to non-controlling interests	(638)	(67)
Comprehensive income (loss) attributable to Blackstone Mortgage Trust, Inc.	$ 80,016	$ (18,869)