Loans and Allowance for Credit Losses - Loans Modified by Class and Delinquency Status (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	$ 1,368
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	318
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	109
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	692	[1]
Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	174
Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	75
Financial Asset, Not Past Due [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	1,191
Financial Asset, Not Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	287
Financial Asset, Not Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	43
Financial Asset, Not Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	668	[1]
Financial Asset, Not Past Due [Member] | Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	125
Financial Asset, Not Past Due [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	68
Financing Receivables 30 To 89 Days Past Due [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	55
Financing Receivables 30 To 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	7
Financing Receivables 30 To 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	11	[1]
Financing Receivables 30 To 89 Days Past Due [Member] | Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	34
Financing Receivables 30 To 89 Days Past Due [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	3
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	122
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	24
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	66
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	13	[1]
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	15
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period excluding forbearance	$ 4

[1] At June 30, 2023, $95 million of loans 30-89 days past due and $20 million of loans 90 days or more past due purchased and that could be purchased from GNMA mortgage pools under delinquent loan repurchase options whose payments are insured by the Federal Housing administration or guaranteed by the United States Department of Veterans Affairs, were classified as current.