v3.26.1
Commitments and contingencies - Commitments - Additional Information (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Commitments and Contingencies Disclosure [Line Items]    
Loans And Leases Receivable Gross Carrying Amount $ 39,703,844,000 $ 39,749,142,000
Maximum Automated Clearing House (ACH) transaction settlement exposure 47,400,000  
Commitments to extend credit    
Commitments and Contingencies Disclosure [Line Items]    
Reserve of potential losses associated with unfunded loan commitments 15,000,000 14,000,000
Noncredit commitment    
Commitments and Contingencies Disclosure [Line Items]    
Investments 5,000,000 7,000,000
BVI    
Commitments and Contingencies Disclosure [Line Items]    
Total concentration of risk 0  
BVI | Retail and commerical loans    
Commitments and Contingencies Disclosure [Line Items]    
Loans And Leases Receivable Gross Carrying Amount 197,000,000 195,000,000
Insured or guaranteed by the U.S. Government or its agencies | Commercial Loans    
Commitments and Contingencies Disclosure [Line Items]    
Loans And Leases Receivable Gross Carrying Amount 84,800,000 80,500,000
Insured or guaranteed by the U.S. Government or its agencies | Residential mortgage loans    
Commitments and Contingencies Disclosure [Line Items]    
Loans And Leases Receivable Gross Carrying Amount 2,600,000,000 2,500,000,000
PR Government direct exposure    
Commitments and Contingencies Disclosure [Line Items]    
Total concentration of risk 389,688,000 391,000,000
Outstanding concentration of risk $ 340,288,000 342,000,000
Exposure Municipal Loans And Securities 77.00%  
PR Government direct exposure | Loans    
Commitments and Contingencies Disclosure [Line Items]    
Outstanding concentration of risk $ 333,167,000 333,000,000
PR Government direct exposure | Securities Investment    
Commitments and Contingencies Disclosure [Line Items]    
Outstanding concentration of risk 7,121,000 9,000,000
PR Government Indirect Exposure    
Commitments and Contingencies Disclosure [Line Items]    
Outstanding concentration of risk 201,000,000 209,000,000
Loans and Leases Receivable, Consumer, Mortgage with PRHA 166,000,000 167,000,000
PR Government Indirect Exposure | Commercial Loans | BPPR    
Commitments and Contingencies Disclosure [Line Items]    
Loans And Leases Receivable Gross Carrying Amount 178,400,000 178,600,000
PR Government Indirect Exposure | PR Housing Bonds backed by second mortgage loans    
Commitments and Contingencies Disclosure [Line Items]    
Outstanding concentration of risk 35,000,000 36,000,000
USVI Government Direct Exposure | From USVI Government And Public Corporations    
Commitments and Contingencies Disclosure [Line Items]    
Total concentration of risk $ 28,000,000 $ 28,000,000