Investment Securities - Amortized Cost and Estimated Fair Value of Collateralized Mortgage Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Amortized Cost And Fair Value Debt Securities [Abstract]
Collateralized mortgage obligations, Amortized cost	$ 372,373	$ 61,980
Collateralized mortgage obligations, Estimated fair value	$ 327,981	$ 57,763

Fair value of collateralized mortgage obligations included in mortgage-backed securities.

No definition available.

Name:	mtb_CollateralizedMortgageObligationsEstimatedFairValue
Namespace Prefix:	mtb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant