Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, Other Assets and Other Liabilities Disclosure [Abstract]
Accrued interest receivable	$ 206,227	$ 214,835
Loan portfolio payments held by servicer	114,247	152,423
Derivative assets	25,922	1,890
Accounts receivable and other assets	6,079	2,420
Prepaid expenses	1,257	1,020
Collateral deposited under derivative agreements	0	103,500
Total	$ 353,732	$ 476,088