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Regulatory Matters - Additional Information (Detail) $ in Billions	Dec. 31, 2024 USD ($)	Oct. 01, 2024
Regulatory Capital Requirements under Banking Regulations [Abstract]
Funds available for payment of dividends to M&T from banking subsidiaries	$ 2.3
Capital conservation buffer	2.50%
Capital conservation buffer ratio effective		0.038
CET1 capital requirement ratio	8.30%

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Capital Conservation Buffer Ratio

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Capital Conservation Buffer Ratio Effective

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Common Equity Tier One Capital Requirement Ratio

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Funds Available For Payment Of Dividends To Parent Company From Banking Subsidiaries

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Regulatory Capital Requirements under Banking Regulations

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