Credit Quality and the Allowance for Loan and Lease Losses - Summary of Portfolio Loans, by Class, that Received Payment Deferrals or Forbearances (Details) $ in Millions	3 Months Ended
	Jun. 30, 2020 USD ($) loan
Commercial
Financing Receivable, Impaired [Line Items]
Loans classified as TDR	$ 28
Consumer | Home equity
Financing Receivable, Impaired [Line Items]
Loans classified as TDR	$ 12
COVID-19 Hardship Relief Programs
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	119,361
Principal Balance of Loans Enrolled in Programs	$ 6,710
COVID-19 Hardship Relief Programs | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	117
COVID-19 Hardship Relief Programs | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 125
COVID-19 Hardship Relief Programs | Commercial | Commercial and industrial loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	3,240
Principal Balance of Loans Enrolled in Programs	$ 1,442
COVID-19 Hardship Relief Programs | Commercial | Commercial and industrial loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	1
COVID-19 Hardship Relief Programs | Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	605
Principal Balance of Loans Enrolled in Programs	$ 612
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage owner-occupied loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	0
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	187
Principal Balance of Loans Enrolled in Programs	$ 1,021
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage nonowner-occupied loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	0
COVID-19 Hardship Relief Programs | Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0
COVID-19 Hardship Relief Programs | Commercial | Commercial construction loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	31
Principal Balance of Loans Enrolled in Programs	$ 365
COVID-19 Hardship Relief Programs | Commercial | Commercial construction loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	1
COVID-19 Hardship Relief Programs | Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0
COVID-19 Hardship Relief Programs | Commercial | Commercial leases
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	93
Principal Balance of Loans Enrolled in Programs	$ 111
COVID-19 Hardship Relief Programs | Commercial | Commercial leases | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	0
COVID-19 Hardship Relief Programs | Commercial | Commercial leases | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0
COVID-19 Hardship Relief Programs | Residential Mortgage
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	7,290
Principal Balance of Loans Enrolled in Programs	$ 1,472
COVID-19 Hardship Relief Programs | Residential Mortgage | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	55
COVID-19 Hardship Relief Programs | Residential Mortgage | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 112
COVID-19 Hardship Relief Programs | Consumer | Home equity
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	3,409
Principal Balance of Loans Enrolled in Programs	$ 231
COVID-19 Hardship Relief Programs | Consumer | Home equity | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	10
COVID-19 Hardship Relief Programs | Consumer | Home equity | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 10
COVID-19 Hardship Relief Programs | Consumer | Indirect secured consumer loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	58,716
Principal Balance of Loans Enrolled in Programs	$ 1,179
COVID-19 Hardship Relief Programs | Consumer | Indirect secured consumer loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	40
COVID-19 Hardship Relief Programs | Consumer | Indirect secured consumer loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 1
COVID-19 Hardship Relief Programs | Consumer | Credit card
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	35,616
Principal Balance of Loans Enrolled in Programs	$ 164
COVID-19 Hardship Relief Programs | Consumer | Credit card | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	7
COVID-19 Hardship Relief Programs | Consumer | Credit card | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 2
COVID-19 Hardship Relief Programs | Consumer | Other consumer loans
Financing Receivable, Impaired [Line Items]
Number of Loans Enrolled in Programs | loan	10,174
Principal Balance of Loans Enrolled in Programs	$ 113
COVID-19 Hardship Relief Programs | Consumer | Other consumer loans | 30-89 days past due
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	3
COVID-19 Hardship Relief Programs | Consumer | Other consumer loans | 90 Days or More
Financing Receivable, Impaired [Line Items]
Balances of Accounts Enrolled in Programs that Were Past Due Prior to Pandemic	$ 0