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Segment Information - Information about Company's Segments (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting [Abstract]
Taxable-equivalent adjustment	$ 23,642,000mtb_TaxableEquivalentAdjustment	$ 24,971,000mtb_TaxableEquivalentAdjustment	$ 26,391,000mtb_TaxableEquivalentAdjustment