Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Liabilities [Abstract]
Accrued dividends payable	$ 76,530	$ 66,888
Accrued interest payable	25,588	14,162
Accrued management and incentive fees payable	18,586	14,284
Accounts payable and other liabilities	4,583	2,125
Derivative liabilities	2,925	4,911
Secured debt repayments pending servicer remittance		38,456
Total	$ 128,212	$ 140,826