Derivative and Credit Risk Transfer Strip Assets and Liabilities - Summary of Derivative and Credit Risk Transfer Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets	$ 81,844	$ 177,984
Derivative and credit risk transfer strip assets	81,844	177,984
Derivative liabilities	2,676	4,689
Credit risk transfer strip liabilities	13,475	46,692
Total derivative and credit risk transfer strip liabilities	$ 16,151	$ 51,381