XML 12 R1.htm IDEA: XBRL DOCUMENT v3.10.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 31, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
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   140,357,696