v3.26.1
Loans and allowance for loan losses - Loan Modification Activities to Borrowers Experiencing Financial Difficulty on Financing Receivables (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 514,000 $ 472,000 $ 977,000 $ 986,000
Percent of Total Loan Class 0.36% 0.35% 0.68% 0.73%
Guaranteed by Government-Related Entities        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 48,000 $ 36,000 $ 62,000 $ 70,000
Commercial and industrial        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 116,000 $ 87,000 $ 213,000 $ 223,000
Percent of Total Loan Class 0.18% 0.14% 0.32% 0.36%
Commercial | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 144,000 $ 319,000 $ 418,000 $ 452,000
Percent of Total Loan Class 0.68% 1.58% 1.97% 2.24%
Residential builder and developer | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 0 $ 0 $ 9,000 $ 0
Percent of Total Loan Class 0.00% 0.00% 7.85% 0.00%
Other commercial construction | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 187,000 $ 12,000 $ 249,000 $ 214,000
Percent of Total Loan Class 5.94% 27.00% 7.92% 5.03%
Residential | Residential real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 58,000 $ 44,000 $ 79,000 $ 87,000
Percent of Total Loan Class 0.23% 18.00% 0.31% 36.00%
Home equity lines and loans (e) | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 1,000 $ 0 $ 1,000 $ 0
Percent of Total Loan Class 0.02% 0.00% 0.02% 0.00%
Recreational finance | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 0 $ 0 $ 0 $ 0
Percent of Total Loan Class 0.00% 0.00% 0.00% 0.00%
Automobile | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 0 $ 0 $ 0 $ 0
Percent of Total Loan Class 0.00% 0.00% 0.00% 0.00%
Other | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 8,000 $ 10,000 $ 8,000 $ 10,000
Percent of Total Loan Class 0.32% 44.00% 0.32% 44.00%
Unfunded Loan Commitment        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 29,000 $ 10,000 $ 45,000 $ 18,000
Term Extension        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 423,000 393,000 764,000 824,000
Term Extension | Commercial and industrial        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 73,000 68,000 136,000 130,000
Term Extension | Commercial | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 120,000 266,000 313,000 399,000
Term Extension | Residential builder and developer | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 9,000 0
Term Extension | Other commercial construction | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 183,000 12,000 245,000 214,000
Term Extension | Residential | Residential real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 39,000 37,000 53,000 71,000
Term Extension | Home equity lines and loans (e) | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Term Extension | Recreational finance | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Term Extension | Automobile | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Term Extension | Other | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 8,000 10,000 8,000 10,000
Other        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 9,000 70,000 23,000 74,000
Other | Commercial and industrial        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 6,000 16,000 9,000 17,000
Other | Commercial | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 1,000 53,000 9,000 53,000
Other | Residential builder and developer | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Other | Other commercial construction | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Other | Residential | Residential real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 2,000 1,000 5,000 4,000
Other | Home equity lines and loans (e) | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Other | Recreational finance | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Other | Automobile | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Other | Other | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Combination of Modification Types        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 82,000 9,000 190,000 88,000
Combination of Modification Types | Commercial and industrial        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 37,000 3,000 68,000 76,000
Combination of Modification Types | Commercial | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 23,000 0 96,000 0
Combination of Modification Types | Residential builder and developer | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Combination of Modification Types | Other commercial construction | Commercial real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 4,000 0 4,000 0
Combination of Modification Types | Residential | Residential real estate        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 17,000 6,000 21,000 12,000
Combination of Modification Types | Home equity lines and loans (e) | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 1,000 0 1,000 0
Combination of Modification Types | Recreational finance | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Combination of Modification Types | Automobile | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period 0 0 0 0
Combination of Modification Types | Other | Consumer        
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]        
Modified in period $ 0 $ 0 $ 0 $ 0