Bank Premises and Equipment - Components of Bank Premises and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Bank premises and equipment, gross	$ 31,059	$ 30,290
Accumulated depreciation and amortization	(21,670)	(19,227)
Total	9,389	11,063
Leasehold improvements
Property, Plant and Equipment [Line Items]
Bank premises and equipment, gross	$ 14,218	14,080
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	3 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	25 years
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Bank premises and equipment, gross	$ 6,333	7,110
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	5 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	10 years
IT equipment
Property, Plant and Equipment [Line Items]
Bank premises and equipment, gross	$ 10,016	8,645
IT equipment | Minimum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	3 years
IT equipment | Maximum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	5 years
Automobiles
Property, Plant and Equipment [Line Items]
Bank premises and equipment, gross	$ 492	$ 455
Automobiles | Minimum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	3 years
Automobiles | Maximum
Property, Plant and Equipment [Line Items]
Expected useful life (years)	5 years