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
Mar. 31, 2026
Mar. 31, 2025
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 558,000 $ 517,000
Percent of Total Loan Class 0.40% 0.38%
Guaranteed by Government-Related Entities    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 14,000 $ 36,000
Commercial and industrial    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 123,000 $ 111,000
Percent of Total Loan Class 0.19% 0.18%
Commercial | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 343,000 $ 131,000
Percent of Total Loan Class 1.71% 0.65%
Residential builder and developer | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 9,000 $ 0
Percent of Total Loan Class 7.86% 0.00%
Other commercial construction | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 61,000 $ 225,000
Percent of Total Loan Class 1.90% 4.53%
Residential | Residential Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 21,000 $ 50,000
Percent of Total Loan Class 0.09% 0.22%
Home equity lines and loans (e) | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 1,000 $ 0
Percent of Total Loan Class 0.01% 0.00%
Recreational finance | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 0 $ 0
Percent of Total Loan Class 0.00% 0.00%
Automobile | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 0 $ 0
Percent of Total Loan Class 0.00% 0.00%
Other | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 0 $ 0
Percent of Total Loan Class 0.00% 0.00%
Unfunded Loan Commitment    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 31,000 $ 9,000
Term Extension    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 423,000 431,000
Term Extension | Commercial and industrial    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 78,000 35,000
Term Extension | Commercial | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 261,000 131,000
Term Extension | Residential builder and developer | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 9,000 0
Term Extension | Other commercial construction | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 61,000 225,000
Term Extension | Residential | Residential Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 14,000 40,000
Term Extension | Home equity lines and loans (e) | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Term Extension | Recreational finance | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Term Extension | Automobile | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Term Extension | Other | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b)    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 21,000 5,000
Other (b) | Commercial and industrial    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 10,000 2,000
Other (b) | Commercial | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 8,000 0
Other (b) | Residential builder and developer | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b) | Other commercial construction | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b) | Residential | Residential Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 3,000 3,000
Other (b) | Home equity lines and loans (e) | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b) | Recreational finance | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b) | Automobile | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Other (b) | Other | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Combination of Modification Types    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 114,000 81,000
Combination of Modification Types | Commercial and industrial    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 35,000 74,000
Combination of Modification Types | Commercial | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 74,000 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
Combination of Modification Types | Other commercial construction | Commercial Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Combination of Modification Types | Residential | Residential Real Estate    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 4,000 7,000
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
Combination of Modification Types | Recreational finance | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Combination of Modification Types | Automobile | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period 0 0
Combination of Modification Types | Other | Consumer    
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]    
Modified in period $ 0 $ 0