Mortgage Banking Income - Components of Gain on Loan Origination and Sale Activities and Mortgage Servicing Fees (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Gain on loan origination and sale activities, net
Gain on sale of mortgage loans and realized gain from derivative financial instruments, net	$ 3,093	$ 15,876
Net change in fair value of loans held for sale and portfolio loans accounted for at fair value	(1,559)	(3,816)
Capitalized residential mortgage loan servicing rights	377	2,797
Net change in fair value of derivative loan commitments and forward loan sale commitments	(647)	(3,864)
Gain on loan origination and sales activities, net	1,264	10,993
Mortgage servicing fees, net
Residential mortgage loan servicing fees	1,277	1,170
Amortization of residential mortgage loan servicing rights	(749)	(812)
Release (provision) to the valuation allowance of mortgage loan servicing rights	135	421
Sub-servicer expenses (1)	(315)
Mortgage servicing fees, net	348	779
Total gain on loan origination and sales activities and mortgage servicing fees, net	$ 1,612	$ 11,772