Regulatory Matters - Additional Information (Detail) $ in Billions	Dec. 31, 2023 USD ($)	Oct. 01, 2023
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Funds available for payment of dividends to M&T from banking subsidiaries	$ 1.7
Capital conservation buffer	2.50%
Capital conservation buffer ratio effective		4
CET1 capital requirement ratio	8.50%