Regulatory Matters - Additional Information (Detail) $ in Millions	Dec. 31, 2022 USD ($)	Oct. 01, 2022	Sep. 30, 2022
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Funds available for payment of dividends to M&T from banking subsidiaries	$ 1,070
Capital conservation buffer	2.50%
Common equity Tier 1 ("CET1") to risk-weighted assets, Minimum			2.50%
Capital conservation buffer ratio effective		4.7