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Segment Information - Summary of Segment Information (Parenthetical) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting [Abstract]
Taxable-equivalent adjustment	$ 5,838,000mtb_TaxableEquivalentAdjustment	$ 5,945,000mtb_TaxableEquivalentAdjustment