Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Deferred Costs, Capitalized, Prepaid, Other Assets and Other Liabilities Disclosure [Abstract]
Accrued interest receivable	$ 181,951	$ 189,569
Loan portfolio payments held by servicer	98,778	68,489
Derivative assets	16,907	7,349
Collateral deposited under derivative agreements	10,370	103,110
Prepaid expenses	1,063	1,067
Accounts receivable and other assets	1,017	1,318
Total	$ 310,086	$ 370,902