Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Other Liabilities [Abstract]
Accrued dividends payable	$ 83,259	$ 76,530
Accrued interest payable	25,522	25,588
Accrued management and incentive fees payable	17,502	18,586
Accounts payable and other liabilities	6,849	4,583
Derivative liabilities	3,992	2,925
Secured debt repayments pending servicer remittance	2,760
Total	$ 139,884	$ 128,212