Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Net income	$ 25,424	$ 279,804	$ 252,319
Other comprehensive income
Unrealized gain on foreign currency remeasurement	798
Unrealized gain on derivative financial instruments		8,367	5,453
Gain on interest rate swaps no longer designated as cash flow hedges		2,481	5,038
Amortization of unrealized gains and losses on securities		(775)	(908)
Amortization of deferred gains and losses on settlement of swaps		(56)	(109)
Other-than-temporary impairments of securities related to fair value adjustments in excess of expected credit losses, net of amortization		688	(326)
Other comprehensive income	798	10,705	9,148
Comprehensive income	26,222	290,509	261,467
Comprehensive (income) loss attributable to non-controlling interests	(10,392)	(98,790)	6,015
Comprehensive income attributable to Blackstone Mortgage Trust, Inc.	$ 15,830	$ 191,719	$ 267,482