Allowance for credit losses - Troubled debt restructurings loan count by type of modification (Details) - loans	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Financing Receivable, Modifications [Line Items]
Loan count	345	765
Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	43	86
Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	73	134
Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	220	508
Other
Financing Receivable, Modifications [Line Items]
Loan count	9	37
Mortgages
Financing Receivable, Modifications [Line Items]
Loan count	251	575
Mortgages | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	3	4
Mortgages | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	31	65
Mortgages | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	217	505
Mortgages | Other
Financing Receivable, Modifications [Line Items]
Loan count	0	1
Commercial | CRE non-owner occupied
Financing Receivable, Modifications [Line Items]
Loan count	2	3
Commercial | CRE non-owner occupied | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Commercial | CRE non-owner occupied | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Commercial | CRE non-owner occupied | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Commercial | CRE non-owner occupied | Other
Financing Receivable, Modifications [Line Items]
Loan count	1	2
Commercial | CRE owner occupied
Financing Receivable, Modifications [Line Items]
Loan count	6	8
Commercial | CRE owner occupied | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	0	1
Commercial | CRE owner occupied | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	5	6
Commercial | CRE owner occupied | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Commercial | CRE owner occupied | Other
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Commercial | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Loan count	3	20
Commercial | Commercial and Industrial | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	2	3
Commercial | Commercial and Industrial | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	0	5
Commercial | Commercial and Industrial | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Commercial | Commercial and Industrial | Other
Financing Receivable, Modifications [Line Items]
Loan count	0	11
Consumer | Credit card
Financing Receivable, Modifications [Line Items]
Loan count	16	46
Consumer | Credit card | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	9	24
Consumer | Credit card | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Consumer | Credit card | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Consumer | Credit card | Other
Financing Receivable, Modifications [Line Items]
Loan count	7	22
Consumer | Personal loans
Financing Receivable, Modifications [Line Items]
Loan count	66	111
Consumer | Personal loans | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	29	54
Consumer | Personal loans | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	36	56
Consumer | Personal loans | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Consumer | Personal loans | Other
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Consumer | Auto Loan
Financing Receivable, Modifications [Line Items]
Loan count		1
Consumer | Auto Loan | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Consumer | Auto Loan | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	0	1
Consumer | Auto Loan | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Consumer | Auto Loan | Other
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Leasing
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Leasing | Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Leasing | Term Extension
Financing Receivable, Modifications [Line Items]
Loan count	0	0
Leasing | Combination of reduction in interest rate and extension of maturity date
Financing Receivable, Modifications [Line Items]
Loan count	1	1
Leasing | Other
Financing Receivable, Modifications [Line Items]
Loan count	0	0