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Variable Interest Entities and Asset Securitizations - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Variable Interest Entity Disclosure [Abstract]      
Carrying value of loans in the Securitization trusts $ 93,000,000mtb_CarryingValueOfLoansInSecuritizationTrusts   $ 98,000,000mtb_CarryingValueOfLoansInSecuritizationTrusts
Combined outstanding principal amount of mortgage-backed securities issued by qualified special purpose trust held by unrelated parties 14,000,000mtb_CombinedOutstandingPrincipalAmountOfMortgageBackedSecuritiesIssuedByQualifiedSpecialPurposeTrustsHeldByUnrelatedParties   15,000,000mtb_CombinedOutstandingPrincipalAmountOfMortgageBackedSecuritiesIssuedByQualifiedSpecialPurposeTrustsHeldByUnrelatedParties
Residential mortgage loans securitized with Ginnie Mae 13,000,000us-gaap_PrincipalAmountOutstandingOnLoansSecuritized 29,000,000us-gaap_PrincipalAmountOutstandingOnLoansSecuritized  
Other assets for its "investment" in the common securities recognized by the company of various trusts 34,000,000mtb_OtherAssetsForItsInvestmentInCommonSecuritiesRecognizedByCompanyOfVariousTrusts   34,000,000mtb_OtherAssetsForItsInvestmentInCommonSecuritiesRecognizedByCompanyOfVariousTrusts
Total assets of real estate partnerships in which the company invested 1,200,000,000us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets   1,200,000,000us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets
Maximum exposure to loss of investments in real estate partnerships 303,000,000mtb_MaximumExposureToLossOfInvestmentsInRealEstatePartnerships   243,000,000mtb_MaximumExposureToLossOfInvestmentsInRealEstatePartnerships
Unfunded commitments included in company's maximum exposure to loss of investments in real estate partnerships 88,000,000mtb_UnfundedCommitmentsIncludedInCompanysMaximumExposureToLossOfInvestmentsInRealEstatePartnerships   56,000,000mtb_UnfundedCommitmentsIncludedInCompanysMaximumExposureToLossOfInvestmentsInRealEstatePartnerships
Investments amortized to income tax expense 10,000,000mtb_AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization 12,000,000mtb_AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization  
Tax credits and other tax benefits recognized $ 14,000,000mtb_AffordableHousingTaxCreditsAndOtherTaxBenefitsAmount $ 17,000,000mtb_AffordableHousingTaxCreditsAndOtherTaxBenefitsAmount