Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Net income	$ 46,093us-gaap_ProfitLoss	$ 13,116us-gaap_ProfitLoss
Other comprehensive income:
Unrealized (loss) gain on foreign currency remeasurement	(16,732)	36
Comprehensive income	29,361	13,152
Comprehensive income attributable to non-controlling interests	(10,700)	(51)
Comprehensive income attributable to Blackstone Mortgage Trust, Inc.	$ 18,661us-gaap_ComprehensiveIncomeNetOfTax	$ 13,101us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount before tax of foreign currency transaction unrealized gain (loss) recognized in the income statement.

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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