Loans and allowance for loan losses - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Loans And Leases Receivable [Line Items]
Loans secured by residential real estate that were in the process of foreclosure	$ 185	$ 182
Percentage loans in the process of foreclosure, serviced by other entities, classified as government guaranteed	55.00%
Financing receivable, accrued interest, before allowance for credit loss	$ 616	627
Commercial and industrial \| Asset Pledged as Collateral without Right
Loans And Leases Receivable [Line Items]
Financing receivable, before allowance for credit loss	22,000
Commercial and industrial \| Asset Pledged as Collateral without Right \| FHLB Facility
Loans And Leases Receivable [Line Items]
Pledged financial instruments		20,700
Commercial Real Estate \| Asset Pledged as Collateral without Right
Loans And Leases Receivable [Line Items]
Financing receivable, before allowance for credit loss	13,600	13,400
Residential Real Estate \| Asset Pledged as Collateral without Right
Loans And Leases Receivable [Line Items]
Financing receivable, before allowance for credit loss	19,600	19,500
Home equity lines and loans (e) \| Consumer \| Asset Pledged as Collateral without Right
Loans And Leases Receivable [Line Items]
Financing receivable, before allowance for credit loss	3,000	3,000
Other \| Consumer \| Asset Pledged as Collateral without Right
Loans And Leases Receivable [Line Items]
Financing receivable, before allowance for credit loss	$ 15,100	$ 15,200

Loans and leases receivable.

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Percentage of loans in the process of foreclosure, serviced by other entities, classified as government guaranteed.

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- Definition

Residential mortgage loans secured by residential real estate in process of foreclosure.

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- Definition

Amount, before allowance for credit loss, of accrued interest on financing receivable.

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Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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