Equity - Schedule of Components of Non-Controlling Interests (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
Restricted cash	$ 10,677	$ 10,096
Accrued interest receivable, prepaid expenses, and other assets	79,323	80,639
Accounts payable, accrued expenses and other liabilities	(66,711)	(56,972)
CT Legacy Partners [Member]
Noncontrolling Interest [Line Items]
Restricted cash	10,677
Accrued interest receivable, prepaid expenses, and other assets	55,176
Accounts payable, accrued expenses and other liabilities	(249)
CT Legacy Partners equity	65,604
Equity interests owned by Blackstone Mortgage Trust, Inc.	(27,287)
Non-controlling interests in CT Legacy Partners	$ 38,317