Loans and the Allowance for Credit Losses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) Contract
Financing Receivable, Recorded Investment [Line Items]
Net deferred fee loan income (costs)	$ (11,500,000)	$ (9,600,000)
Un-accreted discount on purchased loans from acquisitions	13,500,000	18,000,000
Reserve on accrued interest related to CARES Act	$ 100,000
Percentage of national unemployment projection	4.30%
Expected average percentage of national unemployment in future	4.60%
Accrued interest receivable for loans	$ 62,200,000	51,800,000
Accrued interest receivable for loans related to CARES Act	15,600,000	17,000,000
Aggregate amount of residential real estate, home equity and consumer loans classified as substandard	20,000,000	24,800,000
Internally assigned loan grades to residential real estate, home equity and consumer loans	4,600,000	5,900,000
Unfunded commercial loan commitments	21,200,000	$ 25,000,000
TDRs defaulted | Contract		0
Other real estate owned	1,207,000	$ 1,397,000
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Other real estate owned	0	0
Foreclosure proceedings in process on residential real estate loans	4,000,000	$ 4,900,000
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Modification to allowance due to modified loan subsequently defaulting	0
Commercial and Industrial [Member] | Maximum [Member]
Financing Receivable, Recorded Investment [Line Items]
Annual sales of borrowers	100,000,000
Unfunded Loan Commitment [Member]
Financing Receivable, Recorded Investment [Line Items]
Modifications loans	$ 1,800,000