Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	MTB
Entity Registrant Name	M&T BANK CORP
Entity Central Index Key	0000036270
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		131,960,084
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	1-9861
Entity Tax Identification Number	16-0968385
Entity Address, Address Line One	One M & T Plaza
Entity Address, City or Town	Buffalo
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	14203
City Area Code	716
Local Phone Number	635-4000
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $.50 par value
Security Exchange Name	NYSE
Entity Incorporation, State or Country Code	NY
Document Quarterly Report	true
Document Transition Report	false