Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Other Liabilities [Abstract]
Accrued dividends payable	$ 83,259	$ 76,530
Accrued interest payable	25,933	25,588
Accrued management and incentive fees payable	20,984	18,586
Accounts payable and other liabilities	5,631	4,583
Derivative liabilities	4,968	2,925
Total	$ 140,775	$ 128,212