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Loans and allowance for loan losses - Additional Information (Detail) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Loans And Leases Receivable [Line Items] |  |
Amount of foreclosed residential real estate property held | $ 37 | $ 35
Loans secured by residential real estate that were in the process of foreclosure | $ 180 | 173
Percentage loans in the process of foreclosure, serviced by other entities, classified as government guaranteed | 46.00% |
Financing receivable, accrued interest, before allowance for credit loss | $ 619 | 628
Commercial and industrial | Asset Pledged as Collateral without Right |  |
Loans And Leases Receivable [Line Items] |  |
Financing receivable, before allowance for credit loss | 21,100 |
Commercial and industrial | Asset Pledged as Collateral without Right | FHLBs 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 | 13,400 |
Commercial Real Estate | Asset Pledged as Collateral without Right | FHLBs Facility |  |
Loans And Leases Receivable [Line Items] |  |
Pledged financial instruments |  | 14,600
Residential Real Estate | Asset Pledged as Collateral without Right |  |
Loans And Leases Receivable [Line Items] |  |
Financing receivable, before allowance for credit loss | 19,300 |
Residential Real Estate | Asset Pledged as Collateral without Right | FHLBs Facility |  |
Loans And Leases Receivable [Line Items] |  |
Pledged financial instruments |  | 18,600
Home equity lines and loans | Consumer | Asset Pledged as Collateral without Right |  |
Loans And Leases Receivable [Line Items] |  |
Financing receivable, before allowance for credit loss | 2,900 |
Home equity lines and loans | Consumer | Asset Pledged as Collateral without Right | FHLBs Facility |  |
Loans And Leases Receivable [Line Items] |  |
Pledged financial instruments |  | 2,700
Other | Consumer | Asset Pledged as Collateral without Right |  |
Loans And Leases Receivable [Line Items] |  |
Financing receivable, before allowance for credit loss | $ 13,700 |
Other | Consumer | Asset Pledged as Collateral without Right | FHLBs Facility |  |
Loans And Leases Receivable [Line Items] |  |
Pledged financial instruments |  | $ 13,100

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