Acquisitions (Details Textual) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	May 31, 2011 Minimum [Member]	May 31, 2011 Maximum [Member]	May 31, 2011 Wilmington Trust Corporation Acquisition [Member]	Mar. 31, 2011 Wilmington Trust Corporation Acquisition [Member]	Dec. 31, 2011 Wilmington Trust Corporation Acquisition [Member]	May 16, 2011 Wilmington Trust Corporation Acquisition [Member] Office	May 16, 2011 Wilmington Trust Corporation [Member]
Acquisitions (Textual) [Abstract]
Number of banking offices operated										55
Shares of M&T common stock exchanged for each share of Wilmington Trust common stock										0.051372
Common stock issued for acquisition							4,694,486
Common shares issued for acquisition fair value										$ 406,000,000
Assets acquired total										10,800,000,000	10,845,042,000
Loans and leases										6,400,000,000	6,410,430,000
Commercial real estate loans										3,200,000,000
Commercial loans and leases										1,400,000,000
Consumer loans										1,100,000,000
Residential real estate loans										680,000,000
Liabilities										10,000,000,000	10,044,555,000
Deposits										8,900,000,000	8,864,161,000
Value added in shareholders equity due to acquisition										406,000,000
Preferred stock redeemed in connection with Willington Trust acquisition										330,000,000
Intangible Assets Amortization					5 years	7 years
Core deposit and other intangibles										112,000,000
Provision for credit losses	60,000,000	63,000,000	109,000,000	138,000,000				41,000,000
Other- than-temporary impairment									5,000,000
Non taxable gain recorded in connection with acquisition							$ 65,000,000