Commitments and contingencies - Commitments - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure
Loans And Leases Receivable Gross Carrying Amount	$ 31,805,921	$ 29,506,225
Commitments to extend credit
Commitments and Contingencies Disclosure
Reserve of potential losses associated with unfunded loan commitments	7,300	7,900
Noncredit commitment
Commitments and Contingencies Disclosure
Investments	4,800	1,000
Residential mortgage loans
Commitments and Contingencies Disclosure
Loans And Leases Receivable Gross Carrying Amount	1,500,000	1,600,000
SBA loans under PPP program
Commitments and Contingencies Disclosure
Loans And Leases Receivable Gross Carrying Amount	47,000	353,000
BVI | Retail and commerical loans
Commitments and Contingencies Disclosure
Loans And Leases Receivable Gross Carrying Amount	216,000	221,000
Insured or guaranteed by the U.S. Government or its agencies | Commercial Loans
Commitments and Contingencies Disclosure
Loans And Leases Receivable Gross Carrying Amount	71,000	67,000
PR Government direct exposure
Commitments and Contingencies Disclosure
Outstanding concentration of risk	322,217	349,000
Total concentration of risk	$ 365,406	367,000
Exposure Municipal Loans And Securities	74.00%
PR Government direct exposure | Loans
Commitments and Contingencies Disclosure
Outstanding concentration of risk	$ 297,515	319,000
PR Government direct exposure | Loans | Adjustment
Commitments and Contingencies Disclosure
Outstanding concentration of risk	297,000
PR Government direct exposure | Securities Investment
Commitments and Contingencies Disclosure
Outstanding concentration of risk	24,702	30,000
PR Government Indirect Exposure
Commitments and Contingencies Disclosure
Outstanding concentration of risk	256,000	275,000
Loans and Leases Receivable, Consumer, Mortgage with PRHA	214,000	232,000
PR Government Indirect Exposure | PR Housing Bonds backed by second mortgage loans
Commitments and Contingencies Disclosure
Outstanding concentration of risk	42,000	43,000
USVI Government Direct Exposure | From USVI Government And Public Corporations
Commitments and Contingencies Disclosure
Total concentration of risk	$ 29,000	$ 70,000