Equity - Schedule of Components of Non-Controlling Interests (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
Restricted cash	$ 11,392	$ 10,096
Accrued interest receivable, prepaid expenses, and other assets	120,704	80,639
Accounts payable, accrued expenses, and other liabilities	(71,345)	(97,153)
CT Legacy Partners [Member]
Noncontrolling Interest [Line Items]
Restricted cash	11,392
Accrued interest receivable, prepaid expenses, and other assets	62,015
Accounts payable, accrued expenses, and other liabilities	(271)
CT Legacy Partners equity	73,136
Equity interests owned by Blackstone Mortgage Trust, Inc.	(30,419)
Non-controlling interests in CT Legacy Partners	$ 42,717