Allowance for credit losses - Troubled debt restructuring according to their accruing status (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	$ 1,644,647
Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	1,495,309
Non-Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	149,338
Mortgages
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	1,256,766
Mortgages | Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	1,169,976
Mortgages | Non-Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	86,790
Commercial
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	324,425
Commercial | Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	269,784
Commercial | Non-Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	54,641
Leasing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	1,178
Leasing | Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	1,154
Leasing | Non-Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	24
Consumer
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	62,278
Consumer | Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	54,395
Consumer | Non-Accruing
Financing Receivable, Modifications [Line Items]
Accumulated loans modified to borrowers under financial difficulties	7,883
TDR
Financing Receivable, Modifications [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	90,890
TDR | Mortgages
Financing Receivable, Modifications [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	58,819
TDR | Commercial
Financing Receivable, Modifications [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	18,451
TDR | Leasing
Financing Receivable, Modifications [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	43
TDR | Consumer
Financing Receivable, Modifications [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	$ 13,577