Transfers of financial assets and servicing assets - Key economic assumptions used (Details) - Residential Mortgage	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
BPPR
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement
Prepayment speed	5.80%	9.50%	6.90%	7.10%
Weighted average life	8 years 9 months 18 days	7 years 3 months 18 days	8 years 3 months 18 days	8 years 10 months 24 days
Discount rate (annual rate)	10.50%	10.90%	10.50%	10.80%
PB
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement
Prepayment speed	13.70%	21.80%	20.50%	22.10%
Weighted average life	5 years 10 months 24 days	3 years 7 months 6 days	15 years 4 months 24 days	3 years 6 months
Discount rate (annual rate)	10.00%	10.80%	10.90%	10.40%