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Loans and Leases and the Allowance for Credit Losses - Summary of Payment Status of Loans Modified (Parenthetical) (Detail) $ in Millions | Mar. 31, 2024 USD ($)
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
30-89 Days Past Due | $ 121
Past Due 90 Days or More | 64
Guaranteed by Government-Related Entities [Member] |
Accounts, Notes, Loans and Financing Receivable [Line Items] |
30-89 Days Past Due | 30
Past Due 90 Days or More | $ 27

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- Definition Delinquency status of loans and leases receivable modified past due ninety days or more. + References No definition available. + Details
Name: | mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueNinetyDaysOrMore
Namespace Prefix: | mtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Delinquency status of loans and leases receivable modified past due thirty to eighty nine days. + References No definition available. + Details
Name: | mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueThirtyToEightyNineDays
Namespace Prefix: | mtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis=us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |