Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net income	$ 140,414	$ 307,393	$ 285,813
Other comprehensive income
Unrealized gain (loss) on foreign currency translation	87,113	23,920	(44,317)
Realized and unrealized (loss) gain on derivative financial instruments	(59,710)	(5,931)	39,801
Other comprehensive income (loss)	27,403	17,989	(4,516)
Comprehensive income	167,817	325,382	281,297
Comprehensive income attributable to non-controlling interests	(2,744)	(1,826)	(735)
Comprehensive income attributable to Blackstone Mortgage Trust, Inc.	$ 165,073	$ 323,556	$ 280,562