Premises and Equipment - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2009 USD ($) renewal_term	Dec. 31, 2018 USD ($) lease	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Depreciation on premises and equipment		$ 3,706	$ 3,811	$ 3,215
Rental expense, net of rental income		932	870	773
Sale leaseback transaction, lease term	17 years
Sale leaseback transaction, number of automatic renewals | renewal_term	2
Sale leaseback transaction, two automatic lease renewal, period	5 years
Sale leaseback transaction, sale of property, amount	$ 1,200
Sale leaseback transaction, deferred gain	$ 489
Sale leaseback transaction, gain recognized		$ 26	$ 25	$ 25
Facilities
Property, Plant and Equipment [Line Items]
Non-cancelable operating leases having remaining term less than one year | lease		28
Vehicles
Property, Plant and Equipment [Line Items]
Non-cancelable operating leases having remaining term less than one year | lease		6