v3.26.1
Loans and the Allowance for Credit Losses - Additional Information (Detail) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Financing Receivable, Recorded Investment [Line Items]          
Net deferred loan fee income (costs) $ 15,100,000   $ 15,100,000   $ 13,900,000
Un-accreted discount on purchased loans from acquisitions 274,200,000   274,200,000   302,400,000
Reserve on accrued interest related to individually-evaluated loans $ 100,000   $ 100,000    
Percentage of national unemployment projection 4.70%   4.70%    
Expected average percentage of national unemployment in future 5.30%   5.30%    
Accrued interest receivable for loans $ 83,600,000   $ 83,600,000   87,800,000
Aggregate amount of residential real estate, home equity and consumer loans classified as substandard 62,700,000   62,700,000   61,400,000
Internally assigned loan grades to residential real estate, home equity and consumer loans 15,300,000   15,300,000   16,500,000
Unfunded commercial loan commitments 58,500,000   58,500,000   57,100,000
Modifications loans 31,097,000 $ 4,174,000 32,664,000 $ 52,064,000  
Other real estate owned 1,166,000   1,166,000   618,000
Net charge-offs     8,475,000 7,100,000  
Residential Real Estate [Member]          
Financing Receivable, Recorded Investment [Line Items]          
Modifications loans 167,000 2,156,000 198,000 2,642,000  
Other real estate owned 1,000,000   1,000,000   600,000
Foreclosure proceedings in process on residential real estate loans 15,800,000   15,800,000   $ 11,400,000
Net charge-offs     1,128,000 213,000  
90 Days or More Past Due [Member]          
Financing Receivable, Recorded Investment [Line Items]          
Modification to allowance due to modified loan subsequently defaulting 0   0    
Commercial and Industrial [Member]          
Financing Receivable, Recorded Investment [Line Items]          
Modifications loans $ 8,297,000 $ 1,153,000 9,733,000 6,066,000  
Net charge-offs     3,240,000 2,454,000  
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     $ 3,300,000 $ 1,700,000