Allowance for credit losses - Troubled debt restructurings loan count by type of modification (Details) - loans	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable
Loan count	587	466
Mortgages
Financing Receivable
Loan count	408	175
Commercial | Commercial multi-family
Financing Receivable
Loan count	1
Commercial | CRE non-owner occupied
Financing Receivable
Loan count	9	1
Commercial | CRE owner occupied
Financing Receivable
Loan count	22	6
Commercial | Commercial and Industrial
Financing Receivable
Loan count	8	13
Consumer | Credit cards
Financing Receivable
Loan count	66	161
Consumer | Home equity lines of credit
Financing Receivable
Loan count	1	1
Consumer | Personal loans
Financing Receivable
Loan count	64	102
Consumer | Auto Loan
Financing Receivable
Loan count	3	3
Consumer | Other
Financing Receivable
Loan count	4	1
Leasing
Financing Receivable
Loan count	1	3
Reduction in interest rate
Financing Receivable
Loan count	127	252
Reduction in interest rate | Mortgages
Financing Receivable
Loan count	8	2
Reduction in interest rate | Commercial | Commercial multi-family
Financing Receivable
Loan count	0
Reduction in interest rate | Commercial | CRE non-owner occupied
Financing Receivable
Loan count	0	0
Reduction in interest rate | Commercial | CRE owner occupied
Financing Receivable
Loan count	2	0
Reduction in interest rate | Commercial | Commercial and Industrial
Financing Receivable
Loan count	0	1
Reduction in interest rate | Consumer | Credit cards
Financing Receivable
Loan count	52	148
Reduction in interest rate | Consumer | Home equity lines of credit
Financing Receivable
Loan count	0	0
Reduction in interest rate | Consumer | Personal loans
Financing Receivable
Loan count	61	100
Reduction in interest rate | Consumer | Auto Loan
Financing Receivable
Loan count	0	0
Reduction in interest rate | Consumer | Other
Financing Receivable
Loan count	4	1
Reduction in interest rate | Leasing
Financing Receivable
Loan count	0	0
Extension of maturity date
Financing Receivable
Loan count	81	46
Extension of maturity date | Mortgages
Financing Receivable
Loan count	40	26
Extension of maturity date | Commercial | Commercial multi-family
Financing Receivable
Loan count	1
Extension of maturity date | Commercial | CRE non-owner occupied
Financing Receivable
Loan count	9	1
Extension of maturity date | Commercial | CRE owner occupied
Financing Receivable
Loan count	20	6
Extension of maturity date | Commercial | Commercial and Industrial
Financing Receivable
Loan count	8	11
Extension of maturity date | Consumer | Credit cards
Financing Receivable
Loan count	0	0
Extension of maturity date | Consumer | Home equity lines of credit
Financing Receivable
Loan count	0	0
Extension of maturity date | Consumer | Personal loans
Financing Receivable
Loan count	2	1
Extension of maturity date | Consumer | Auto Loan
Financing Receivable
Loan count	1	1
Extension of maturity date | Consumer | Other
Financing Receivable
Loan count	0	0
Extension of maturity date | Leasing
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date
Financing Receivable
Loan count	365	153
Combination of reduction in interest rate and extension of maturity date | Mortgages
Financing Receivable
Loan count	360	147
Combination of reduction in interest rate and extension of maturity date | Commercial | Commercial multi-family
Financing Receivable
Loan count	0
Combination of reduction in interest rate and extension of maturity date | Commercial | CRE non-owner occupied
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date | Commercial | CRE owner occupied
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date | Commercial | Commercial and Industrial
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date | Consumer | Credit cards
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date | Consumer | Home equity lines of credit
Financing Receivable
Loan count	1	1
Combination of reduction in interest rate and extension of maturity date | Consumer | Personal loans
Financing Receivable
Loan count	1	0
Combination of reduction in interest rate and extension of maturity date | Consumer | Auto Loan
Financing Receivable
Loan count	2	2
Combination of reduction in interest rate and extension of maturity date | Consumer | Other
Financing Receivable
Loan count	0	0
Combination of reduction in interest rate and extension of maturity date | Leasing
Financing Receivable
Loan count	1	3
Other
Financing Receivable
Loan count	14	15
Other | Mortgages
Financing Receivable
Loan count	0	0
Other | Commercial | Commercial multi-family
Financing Receivable
Loan count	0
Other | Commercial | CRE non-owner occupied
Financing Receivable
Loan count	0	0
Other | Commercial | CRE owner occupied
Financing Receivable
Loan count	0	0
Other | Commercial | Commercial and Industrial
Financing Receivable
Loan count	0	1
Other | Consumer | Credit cards
Financing Receivable
Loan count	14	13
Other | Consumer | Home equity lines of credit
Financing Receivable
Loan count	0	0
Other | Consumer | Personal loans
Financing Receivable
Loan count	0	1
Other | Consumer | Auto Loan
Financing Receivable
Loan count	0	0
Other | Consumer | Other
Financing Receivable
Loan count	0	0
Other | Leasing
Financing Receivable
Loan count	0	0