Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Other Liabilities [Abstract]
Secured debt repayments pending servicer remittance	$ 91,763	$ 5,372
Accrued dividends payable	58,787	58,615
Accrued management and incentive fees payable	12,921	12,798
Accrued interest payable	11,673	9,049
Accounts payable and other liabilities	1,736	1,985
Total	$ 176,880	$ 87,819