Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Other Liabilities [Abstract]
Secured debt repayments pending servicer remittance	$ 21,669	$ 5,372
Accrued dividends payable	58,793	58,615
Accrued management and incentive fees payable	14,393	12,798
Accrued interest payable	11,690	9,049
Derivative liabilities	6,928	210
Accounts payable and other liabilities	3,264	1,775
Total	$ 116,737	$ 87,819