Debt securities held-to-maturity -Additional Information (Details) - USD ($)	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	$ 6,405,803,000	$ 7,620,074,000
Allowance for credit losses	6,230,000	5,812,000
Total past due
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	0	0
Munis Payable from US Treasure Securities Proceeds
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	0	6,800,000
Obligations of Puerto Rico, States and political subdivisions
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	41,849,000	51,107,000
Allowance for credit losses	6,230,000	5,812,000
Obligations of Puerto Rico, States and political subdivisions | Munis Payable From Real and Personal Property Taxes
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	7,100,000	8,700,000
Obligations of Puerto Rico, States and political subdivisions | Munis Payable From Real and Personal Property Taxes | Pass
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	6,300,000	7,900,000
Obligations of Puerto Rico, States and political subdivisions | Munis Not Guaranteed By Puerto Rico Central Government
Debt Securities, Held-to-maturity
Debt securities held-to-maturity, at amortized cost	$ 34,800,000	$ 36,000,000.0