Allowance for Credit Losses and Credit Quality Information - Schedule of Types of TDR (Details) - loan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	34	40
Total Commercial | Commercial and industrial(1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	1	3
Total Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	3	2
Total Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	1	4
Total Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	10	10
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	19	21
Contractual payment reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	4	12
Contractual payment reduction | Total Commercial | Commercial and industrial(1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	1	0
Contractual payment reduction | Total Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	3	0
Contractual payment reduction | Total Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	3
Contractual payment reduction | Total Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Contractual payment reduction | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	4
Contractual payment reduction | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	5
Maturity date extension
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	1	4
Maturity date extension | Total Commercial | Commercial and industrial(1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	1
Maturity date extension | Total Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Maturity date extension | Total Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	1	0
Maturity date extension | Total Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Maturity date extension | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Maturity date extension | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	3
Discharged in bankruptcy
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	18	11
Discharged in bankruptcy | Total Commercial | Commercial and industrial(1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Discharged in bankruptcy | Total Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Discharged in bankruptcy | Total Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Discharged in bankruptcy | Total Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Discharged in bankruptcy | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	6	3
Discharged in bankruptcy | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	12	8
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	11	13
Other | Total Commercial | Commercial and industrial(1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	2
Other | Total Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	2
Other | Total Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	1
Other | Total Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	0	0
Other | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	4	3
Other | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification total	7	5