Loans and leases and allowance for credit losses - Loan Modification Activities to Borrowers Experiencing Financial Difficulty on Financing Receivables (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) modification
Financing Receivable, Modifications [Line Items]
Number | modification	3,641
Pre- modification Recorded Investment	$ 276
Post-modification	280
Term Extension
Financing Receivable, Modifications [Line Items]
Post-modification	203
Other
Financing Receivable, Modifications [Line Items]
Post-modification	3
Combination of Concession Types
Financing Receivable, Modifications [Line Items]
Post-modification	$ 74
Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Number | modification	231
Pre- modification Recorded Investment	$ 98
Post-modification	98
Commercial Portfolio Segment | Term Extension
Financing Receivable, Modifications [Line Items]
Post-modification	58
Commercial Portfolio Segment | Other
Financing Receivable, Modifications [Line Items]
Post-modification	3
Commercial Portfolio Segment | Combination of Concession Types
Financing Receivable, Modifications [Line Items]
Post-modification	$ 37
Commercial Real Estate | Commercial
Financing Receivable, Modifications [Line Items]
Number | modification	12
Pre- modification Recorded Investment	$ 25
Post-modification	$ 25
Commercial Real Estate | Residential builder and developer
Financing Receivable, Modifications [Line Items]
Number | modification	1
Pre- modification Recorded Investment	$ 0
Post-modification	$ 0
Commercial Real Estate | Other commercial construction
Financing Receivable, Modifications [Line Items]
Number | modification	1
Pre- modification Recorded Investment	$ 0
Post-modification	0
Commercial Real Estate | Term Extension | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification	9
Commercial Real Estate | Term Extension | Residential builder and developer
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Term Extension | Other commercial construction
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Other | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Other | Residential builder and developer
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Other | Other commercial construction
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Combination of Concession Types | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification	16
Commercial Real Estate | Combination of Concession Types | Residential builder and developer
Financing Receivable, Modifications [Line Items]
Post-modification	0
Commercial Real Estate | Combination of Concession Types | Other commercial construction
Financing Receivable, Modifications [Line Items]
Post-modification	$ 0
Residential Real Estate | Residential
Financing Receivable, Modifications [Line Items]
Number | modification	282
Pre- modification Recorded Investment	$ 72
Post-modification	76
Residential Real Estate | Term Extension | Residential
Financing Receivable, Modifications [Line Items]
Post-modification	56
Residential Real Estate | Other | Residential
Financing Receivable, Modifications [Line Items]
Post-modification	0
Residential Real Estate | Combination of Concession Types | Residential
Financing Receivable, Modifications [Line Items]
Post-modification	$ 20
Consumer: | Home equity lines and loans
Financing Receivable, Modifications [Line Items]
Number | modification	144
Pre- modification Recorded Investment	$ 10
Post-modification	$ 10
Consumer: | Recreational finance
Financing Receivable, Modifications [Line Items]
Number | modification	729
Pre- modification Recorded Investment	$ 28
Post-modification	$ 28
Consumer: | Automobile
Financing Receivable, Modifications [Line Items]
Number | modification	2,092
Pre- modification Recorded Investment	$ 42
Post-modification	$ 42
Consumer: | Other
Financing Receivable, Modifications [Line Items]
Number | modification	149
Pre- modification Recorded Investment	$ 1
Post-modification	1
Consumer: | Term Extension | Home equity lines and loans
Financing Receivable, Modifications [Line Items]
Post-modification	9
Consumer: | Term Extension | Recreational finance
Financing Receivable, Modifications [Line Items]
Post-modification	28
Consumer: | Term Extension | Automobile
Financing Receivable, Modifications [Line Items]
Post-modification	42
Consumer: | Term Extension | Other
Financing Receivable, Modifications [Line Items]
Post-modification	1
Consumer: | Other | Home equity lines and loans
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Other | Recreational finance
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Other | Automobile
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Other | Other
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Combination of Concession Types | Home equity lines and loans
Financing Receivable, Modifications [Line Items]
Post-modification	1
Consumer: | Combination of Concession Types | Recreational finance
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Combination of Concession Types | Automobile
Financing Receivable, Modifications [Line Items]
Post-modification	0
Consumer: | Combination of Concession Types | Other
Financing Receivable, Modifications [Line Items]
Post-modification	$ 0