Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Deferred Costs, Capitalized, Prepaid, Other Assets and Other Liabilities Disclosure [Abstract]
Accrued interest receivable	$ 188,844	$ 189,569
Loan portfolio payments held by servicer	49,087	68,489
Derivative assets	12,689	7,349
Collateral deposited under derivative agreements	9,020	103,110
Accounts receivable and other assets	674	1,318
Prepaid expenses	592	1,067
Total	$ 260,906	$ 370,902