Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Nonaccrual [Line Items]
Number of operating segments | segment	1
Number of reportable segments | segment	1
Total stockholders’ equity	$ 763,784,000	$ 725,263,000	$ 623,739,000	$ 583,122,000
Debt securities, non-accrual status, past due payment period	30 days
Debt securities, accrual status, sustained interest payment period	6 months
Accrued interest receivable, securities	$ 3,300,000
Principal and interest default period	90 days
Residential mortgage loans are placed on non-accrual status at the time principal and interest period	90 days
Period of principal and interest payments in arrears for open-end consumer loans are reviewed for charge-off	4 months
Non-accrual asset satisfactory payments period	6 months
Non-accrual loans with recorded investment, minimum amount		500,000
Maximum amount of individual impaired commercial loans that places into homogeneous pool for collective evaluation	$ 500,000
Maximum amount of individual impaired loans that places into Homogeneous pool for collective evaluation	500,000
Amount of loans sold that are being serviced for others	34,100,000	18,600,000
Originated mortgage servicing rights	129,000	43,000
Goodwill	156,277,000	156,277,000
Bank owned life insurance	115,115,000	112,392,000
Income on bank owned life insurance	2,657,000	2,740,000	3,256,000
Company's liability to trusts including investments	$ 30,000,000.0
Percentage of capital permitted for trust preferred securities	25.00%
Cumulated adjustment for adoption of ASU
Financing Receivable, Nonaccrual [Line Items]
Total stockholders’ equity		$ (3,395,000)	$ 125,000
Non-owner occupied commercial
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	10 years
Financing receivable, amortization schedule term	25 years
Owner occupied commercial
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	10 years
Financing receivable, amortization schedule term	25 years
Multifamily
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	10 years
Financing receivable, amortization schedule term	30 years
Non-owner occupied residential
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	10 years
Financing receivable, amortization schedule term	25 years
Commercial, industrial and other | Minimum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	1 year
Commercial, industrial and other | Maximum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	7 years
Construction | Minimum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	1 year
Construction | Maximum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	3 years
Equipment finance | Minimum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	3 years
Equipment finance | Maximum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	5 years
Residential mortgage | Minimum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	15 years
Residential mortgage | Maximum
Financing Receivable, Nonaccrual [Line Items]
Financing receivable contract term	30 years