Leases - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	$ 4,800,000		$ 4,800,000
Operating lease, liabilities	5,202,000		5,202,000
Operating lease, expense	$ 343,000		$ 661,000
Operating lease, weighted average discount rate	2.68%		2.68%
Additional operating lease, ROU assets	$ 242,000
Additional operating lease, liabilities	242,000
Right of use asset amortization	298,000		$ 626,000
Short-term lease expense	$ 31,000		$ 62,000
Rent expense		$ 259,000,000		$ 542,000,000
Minimum [Member]
Lessee Lease Description [Line Items]
Remaining lease terms			1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Remaining lease terms			23 years