Leases - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Lessee Lease Description [Line Items]
Operating lease, option to extend			Operating leases relate primarily to bank branches, office space and license agreements with remaining lease terms of generally 1 to 23 years, which includes options for multiple extensions, with a weighted-average lease term of 7 years.
Operating lease, existence of option to extend			true
Operating lease, weighted average lease term	7 years		7 years
Operating lease, ROU assets	$ 4,600,000		$ 4,600,000
Operating lease, liabilities	4,936,000		4,936,000
Operating lease, expense	$ 326,000		$ 987,000
Operating lease, weighted average discount rate	2.68%		2.68%
Right of use asset amortization	$ 243,000		$ 869,000
Short-term lease expense	$ 31,000		$ 93,000
Rent expense		$ 294,000		$ 836,000
Minimum [Member]
Lessee Lease Description [Line Items]
Remaining lease terms			1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Remaining lease terms			23 years