Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Liabilities [Abstract]
Accrued dividends payable	$ 77,913	$ 76,530
Accrued interest payable	28,904	25,588
Accrued management and incentive fees payable	19,790	18,586
Accounts payable and other liabilities	3,950	4,583
Derivative liabilities	1,726	2,925
Total	$ 132,283	$ 128,212