Allowance for credit losses - Allowance for loan losses - Additional Information (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($) loans NumberOfCustomer	Mar. 31, 2020	Jun. 30, 2019 loans	Jun. 30, 2020 USD ($) NumberOfCustomer loans	Jun. 30, 2019 loans	Dec. 31, 2019 USD ($)
Financing Receivable
Troubled debt restructurings	$ 1,599,178			$ 1,599,178		$ 1,587,684
Aggregated unpaid principal balance						1,223,205
Loan count | loans	238		203	366	336
Allowance for credit loss calculation assumption adopted	In order to calculate the ACL for the second quarter, the Corporation selected Moody’s Analytics June Baseline scenario. This scenario exhibits greater deterioration in the economy at its peak, with US and PR economic activity declining by 33.4% and 24.6% during the second quarter of 2020, respectively, while unemployment rate increases to 14.0% and 14.4% for the US and PR, respectively. This scenario includes a significant pickup in economic activity during the third quarter of 2020, in part driven by federal stimulus and the resumption of economic activity in the different states. However, from the fourth quarter of 2020 through the second quarter of 2021, the economy experiences a slow, U-Shaped recovery. Unemployment levels remained elevated during 2021 with the unemployment rate averaging 9.3% and 11.5% for the US and PR, respectively. Subsequent changes to this forecast and related estimates will be reflected in the provision for credit losses in future periods.	As part of the first quarter’s ACL calculation, the Corporation selected Moody’s Analytics March 27th S3 Downside Scenario. This scenario, which contemplates a double-dip recession, had the recession peaking during the second quarter of 2020. During that quarter US real GDP declined by 25%, and the US unemployment rate increased to 13%. This scenario had a similar path for the PR economy in the second quarter of 2020 where economic activity decreased by 18%, and the unemployment rate peaked at 13.5%. After a modest rebound in the third quarter of 2020, the economy continued its decline through the first half of 2021 with a sustained recovery beginning during the second quarter of 2021. The unemployment rate for 2021 averaged 9.8% and 11.7% for the US and PR, respectively.
COVID-19 | Retail
Financing Receivable
Number of customers | NumberOfCustomer	116,226			116,226
Loan receivables granted for moratorium	$ 3,900,000			$ 3,900,000
COVID-19 | Commercial Loans
Financing Receivable
Number of customers | NumberOfCustomer	5,003			5,003
Loan receivables granted for moratorium	$ 4,100,000			$ 4,100,000
Commercial and Industrial
Financing Receivable
Aggregated unpaid principal balance						91,866
Mortgages
Financing Receivable
Troubled debt restructurings	$ 1,155,785			$ 1,155,785		1,139,597
Aggregated unpaid principal balance						624,368
Loan count | loans	101		11	148	19
Mortgages | Guaranteed by us sponsored entities
Financing Receivable
Aggregated unpaid principal balance	$ 642,000			$ 642,000		625,000
Commercial
Financing Receivable
Troubled debt restructurings	348,725			348,725		349,448
Outstanding commitments to lend additional funds to debtors owing receivables whose terms have been modified in troubled debt restructurings	$ 13,000			$ 13,000		$ 14,000
Commercial | Commercial and Industrial
Financing Receivable
Loan count | loans	1		2	3	3