Regulatory Matters - Additional Information (Detail) - USD ($) $ in Billions	Dec. 31, 2021	Jan. 01, 2020
Regulatory Capital Requirements [Abstract]
Funds available for payment of dividends to M&T from banking subsidiaries	$ 1.6
Capital conservation buffer		2.50%

Amount of dividends available for payment to parent company after computation of banking subsidiaries earnings for the current year and preceding two years.

No definition available.

Name:	mtb_FundsAvailableForPaymentOfDividendsToParentCompanyFromBankingSubsidiaries
Namespace Prefix:	mtb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant