v3.26.1
Loans and allowance for loan losses - Summary of Payment Status of Loans Modified (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Mar. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost $ 1,253,000 $ 1,292,000
Guaranteed by Government-Related Entities    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Modified past due 30-89 days 31,000 29,000
Modified past due 90 days or more 51,000 34,000
Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 1,051,000 1,108,000
30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 118,000 117,000
Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 84,000 67,000
Commercial and industrial    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 225,000 313,000
Commercial and industrial | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 198,000 293,000
Commercial and industrial | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 13,000 3,000
Commercial and industrial | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 14,000 17,000
Commercial Real Estate | Commercial    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 673,000 468,000
Commercial Real Estate | Commercial | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 626,000 419,000
Commercial Real Estate | Commercial | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 31,000 49,000
Commercial Real Estate | Commercial | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 16,000 0
Commercial Real Estate | Residential builder and developer    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 12,000 1,000
Commercial Real Estate | Residential builder and developer | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 12,000 1,000
Commercial Real Estate | Residential builder and developer | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Commercial Real Estate | Residential builder and developer | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Commercial Real Estate | Other commercial construction    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 152,000 328,000
Commercial Real Estate | Other commercial construction | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 120,000 289,000
Commercial Real Estate | Other commercial construction | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 32,000 30,000
Commercial Real Estate | Other commercial construction | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 9,000
Residential Real Estate | Residential    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 177,000 180,000
Residential Real Estate | Residential | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 89,000 104,000
Residential Real Estate | Residential | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 34,000 35,000
Residential Real Estate | Residential | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 54,000 41,000
Consumer | Home equity lines and loans (e)    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 2,000 1,000
Consumer | Home equity lines and loans (e) | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 2,000 1,000
Consumer | Home equity lines and loans (e) | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Home equity lines and loans (e) | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Recreational finance    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 1,000 1,000
Consumer | Recreational finance | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 1,000 1,000
Consumer | Recreational finance | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Recreational finance | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Automobile    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Automobile | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Automobile | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Automobile | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 0 0
Consumer | Other    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 11,000 0
Consumer | Other | Current    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 3,000 0
Consumer | Other | 30-89 Days Past Due    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost 8,000 0
Consumer | Other | Accruing Loans Past Due 90 Days or More    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amortized cost $ 0 $ 0