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, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable
Loan count	345	705	765	1,292
Reduction in interest rate
Financing Receivable
Loan count	43	114	86	241
Extension of maturity date
Financing Receivable
Loan count	73	105	134	186
Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	220	463	508	828
Other
Financing Receivable
Loan count	9	23	37	37
Mortgages
Financing Receivable
Loan count	251	511	575	919
Mortgages | Reduction in interest rate
Financing Receivable
Loan count	3	14	4	22
Mortgages | Extension of maturity date
Financing Receivable
Loan count	31	39	65	79
Mortgages | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	217	458	505	818
Mortgages | Other
Financing Receivable
Loan count	0	0	1	0
Commercial | Commercial multi-family
Financing Receivable
Loan count		1		2
Commercial | Commercial multi-family | Reduction in interest rate
Financing Receivable
Loan count		0		0
Commercial | Commercial multi-family | Extension of maturity date
Financing Receivable
Loan count		0		1
Commercial | Commercial multi-family | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count		1		1
Commercial | Commercial multi-family | Other
Financing Receivable
Loan count		0		0
Commercial | CRE non-owner occupied
Financing Receivable
Loan count	2		3	9
Commercial | CRE non-owner occupied | Reduction in interest rate
Financing Receivable
Loan count	0	0	0	0
Commercial | CRE non-owner occupied | Extension of maturity date
Financing Receivable
Loan count	1	0	1	9
Commercial | CRE non-owner occupied | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	0	0	0	0
Commercial | CRE non-owner occupied | Other
Financing Receivable
Loan count	1	0	2	0
Commercial | CRE owner occupied
Financing Receivable
Loan count	6	9	8	31
Commercial | CRE owner occupied | Reduction in interest rate
Financing Receivable
Loan count	0	1	1	3
Commercial | CRE owner occupied | Extension of maturity date
Financing Receivable
Loan count	5	3	6	23
Commercial | CRE owner occupied | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	1	3	1	3
Commercial | CRE owner occupied | Other
Financing Receivable
Loan count	0	2	0	2
Commercial | Commercial and Industrial
Financing Receivable
Loan count	3	7	20	15
Commercial | Commercial and Industrial | Reduction in interest rate
Financing Receivable
Loan count	2	1	3	1
Commercial | Commercial and Industrial | Extension of maturity date
Financing Receivable
Loan count	0	0	5	8
Commercial | Commercial and Industrial | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	1	0	1	0
Commercial | Commercial and Industrial | Other
Financing Receivable
Loan count	0	6	11	6
Consumer | Credit card
Financing Receivable
Loan count	16	51	46	117
Consumer | Credit card | Reduction in interest rate
Financing Receivable
Loan count	9	37	24	89
Consumer | Credit card | Extension of maturity date
Financing Receivable
Loan count	0	0	0	0
Consumer | Credit card | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	0	1	0	1
Consumer | Credit card | Other
Financing Receivable
Loan count	7	13	22	27
Consumer | Home equity lines of credit
Financing Receivable
Loan count		1		2
Consumer | Home equity lines of credit | Reduction in interest rate
Financing Receivable
Loan count		0		0
Consumer | Home equity lines of credit | Extension of maturity date
Financing Receivable
Loan count		1		1
Consumer | Home equity lines of credit | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count		0		1
Consumer | Home equity lines of credit | Other
Financing Receivable
Loan count		0		0
Consumer | Personal loans
Financing Receivable
Loan count	66	122	111	186
Consumer | Personal loans | Reduction in interest rate
Financing Receivable
Loan count	29	59	54	120
Consumer | Personal loans | Extension of maturity date
Financing Receivable
Loan count	36	61	56	63
Consumer | Personal loans | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	0	0	0	1
Consumer | Personal loans | Other
Financing Receivable
Loan count	1	2	1	2
Consumer | Auto Loan
Financing Receivable
Loan count		1	1	4
Consumer | Auto Loan | Reduction in interest rate
Financing Receivable
Loan count	0	0	0	0
Consumer | Auto Loan | Extension of maturity date
Financing Receivable
Loan count	0	1	1	2
Consumer | Auto Loan | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	0	0	0	2
Consumer | Auto Loan | Other
Financing Receivable
Loan count	0	0	0	0
Consumer | Other
Financing Receivable
Loan count		2		6
Consumer | Other | Reduction in interest rate
Financing Receivable
Loan count		2		6
Consumer | Other | Extension of maturity date
Financing Receivable
Loan count		0		0
Consumer | Other | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count		0		0
Consumer | Other | Other
Financing Receivable
Loan count		0		0
Leasing
Financing Receivable
Loan count	1		1	1
Leasing | Reduction in interest rate
Financing Receivable
Loan count	0	0	0	0
Leasing | Extension of maturity date
Financing Receivable
Loan count	0	0	0	0
Leasing | Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	1	0	1	1
Leasing | Other
Financing Receivable
Loan count	0	0	0	0