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Regulatory Matters - Summary of Required Minimum and Well Capitalized Capital Ratios (Detail)
Dec. 31, 2023
M&T (Consolidated) [Member]  
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]  
CET1 to RWA, Minimum 4.50%
Tier 1 capital to RWA, Minimum 0.060
Total capital to RWA, Minimum 0.080
Leverage - Tier 1 capital to average total assets, as defined 0.040
Tier 1 capital to RWA, Well capitalized 0.060
Total capital to RWA, Well capitalized 0.100
Bank Subsidiaries [Member]  
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]  
CET1 to RWA, Minimum 4.50%
Tier 1 capital to RWA, Minimum 0.060
Total capital to RWA, Minimum 0.080
Leverage - Tier 1 capital to average total assets, as defined 0.040
CET1 to RWA, Well Capitalized 6.50%
Tier 1 capital to RWA, Well capitalized 0.080
Total capital to RWA, Well capitalized 0.100
Leverage - Tier 1 capital to average total assets, as defined 0.050