Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	M&T BANK CORPORATION
Entity Central Index Key	0000036270
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 22,178,197,910
Entity Common Stock, Shares Outstanding		130,436,633
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock, $.50 par value
Trading Symbol	MTB
Security Exchange Name	NYSE
Entity File Number	1-9861
Entity Incorporation, State or Country Code	NY
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
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference [Text Block]	(1) Portions of the Proxy Statement for the 2020 Annual Meeting of Shareholders of M&T Bank Corporation in Parts II and III.