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Regulatory Matters - Additional Information (Detail) - USD ($)
Dec. 31, 2015
Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Funds available for payment of dividends to M&T from banking subsidiaries $ 1,700,000,000  
Required subsidiary noninterest-earning reserves against certain deposit liabilities $ 664,586,000 $ 555,575,000
Minimum "Tier 1 capital" ratio required for capital adequacy 4.00%  
Minimum "Total capital" ratio required for capital adequacy 8.00%  
Minimum "Leverage" ratio to be considered well capitalized 4.00%  
Common equity Tier 1 to risk-weighted assets 4.50%  
Tier 1 capital to risk-weighted assets 6.00%  
Total capital to risk-weighted assets 8.00%  
Minimum [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Consolidated assets required per Federal Reserve Board to submit annual capital plans $ 50,000,000,000