Servicing - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Transfers And Servicing [Abstract]
Loans serviced for others unpaid principal amount	$ 377.5	$ 303.9
Capitalized service right assets included in other assets	3.3	2.6
Fair market value of the capitalized servicing rights	$ 3.5	$ 2.9
Prepayment rate	24.10%	14.10%
Discount yield	2.38%	5.42%