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Fair Value Measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Parenthetical) (Detail) | 3 Months Ended | 12 Months Ended
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Mar. 31, 2024 | Dec. 31, 2023
Fair Value Disclosures [Abstract] |  |
Weighted average commitment expirations, percentage | 8.00% | 5.00%

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- Definition Weighted average commitment expirations. + References No definition available. + Details
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Namespace Prefix: | mtb_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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