Other Assets and Liabilities - Summary of Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accrued dividends payable	$ 91,159	$ 91,004
Accrued interest payable	22,116	20,548
Accrued management and incentive fees payable	19,207	19,158
Derivative liabilities	13,466	58,915
Current expected credit loss reserve for unfunded loan commitments	172,100	173,549	$ 112,694	$ 0
Secured debt repayments pending servicer remittance	6,338	0
Accounts payable and other liabilities	3,784	2,671
Total	167,091	202,327
Unfunded Loan Commitments [Member]
Current expected credit loss reserve for unfunded loan commitments	$ 11,021	$ 10,031	$ 22,536	$ 0