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Income Taxes - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2024 USD ($) state
Income Tax Disclosure [Abstract] |
Allowance for credit loss with no federal tax provision | $ | $ 137
Number of state and local jurisdictions where company files income tax returns | state | 40

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- Definition Allowance For Credit Loss With No Federal Income Tax Allowance Provision + References No definition available. + Details
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- Definition Number Of State And Local Jurisdictions Where Company Files Income Tax Returns + References No definition available. + Details
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Namespace Prefix: | mtb_
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Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration