Segment Information - Additional Information (Detail)	12 Months Ended
Dec. 31, 2020
Segment Reporting [Abstract]
Percent of maximum revenue from single customer on total revenues	10.00%

Maximum percentage of total consolidated revenues generated from a single external customer.

No definition available.

Name:	mtb_PercentOfMaximumRevenueFromSingleCustomerOnRevenue
Namespace Prefix:	mtb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration