Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net income	$ 76,867	$ 61,116
Other comprehensive income
Unrealized gain on foreign currency translation	5,414	10,738
Realized and unrealized loss on derivative financial instruments	(1,948)	(2,935)
Other comprehensive income	3,466	7,803
Comprehensive income	80,333	68,919
Comprehensive income attributable to non-controlling interests	(302)	(158)
Comprehensive income attributable to Blackstone Mortgage Trust, Inc.	$ 80,031	$ 68,761