Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 11, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
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			$ 18,124,066,420
Entity Common Stock, Shares Outstanding		129,034,484
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
ICFR Auditor Attestation Flag	true
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Buffalo, NY, United States
Documents Incorporated by Reference [Text Block]	Portions of the Proxy Statement for the 2022 Annual Meeting of Shareholders of M&T Bank Corporation in Parts II and III.