Other income and other expense - Additional Information (Detail)	12 Months Ended
Dec. 31, 2012
Component of Operating Other Cost and Expense [Line Items]
Minimum percentage of interest income and other income for separate disclosure	1.00%

Minimum percentage of interest income and other income for separate disclosure.

No definition available.

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