Accelerated amortization of preferred stock discount as per redemption. Accelerated Amortization Of Preferred Stock Discount As Per Redemption Accelerated amortization of preferred stock discount as per redemption Accounting Policies [Line Items] Accounting Policies [Line Items] Accounting Policies [Line Items] Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract] Outstanding principal and carrying value of acquired loans recorded at fair value Accrued Investment Income Receivable Accrued interest receivable Accumulated Defined Benefit Plans Adjustment [Member] Defined benefit plans [Member] Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] Cash flow hedges [Member] Accumulated net unrealized investment gain loss all other. Accumulated Net Unrealized Investment Gain Loss All Other [Member] Investment securities All other [Member] Accumulated net unrealized investment gain loss with OTTI. Accumulated Net Unrealized Investment Gain Loss With Otti [Member] Investment securities With OTTI [Member] Accumulated other comprehensive income (loss). Accumulated Other Comprehensive Income Loss [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss Net Of Tax Ending Balance Beginning Balance Accumulated other comprehensive income (loss), net Accumulated Other Comprehensive Income [Member] Accumulated other comprehensive income (loss), net [Member] Accumulated Translation Adjustment [Member] Foreign currency translation adjustment [Member] Acquired financing receivable. Acquired Financing Receivable [Member] Acquired [Member] Acquired Finite Lived Intangible Assets Weighted Average Useful Life Intangible Assets Amortization Acquired loans at fair value carrying amount. Acquired Loans At Fair Value Carrying Amount Carrying Amount Acquired loans at fair value outstanding principal. Acquired Loans At Fair Value Outstanding Principal Outstanding principal balance Acquired loans. Acquired Loans [Member] Acquired Loans [Member] Acquisition common stock shares exchanged per share of acquiree common stock. Acquisition Common Stock Shares Exchanged Per Share Of Acquiree Common Stock Shares of M&T common stock exchanged for each share of Wilmington Trust common stock Acquisitions [Axis] Acquisitions [Axis] Acquisitions [Axis] Acquisitions [Domain] Acquisitions [Domain] Acquisitions [Domain] Additional Collateral Aggregate Fair Value Maximum amount of additional collateral required to post to counterparties Additional Paid In Capital Additional paid-in capital Additional Paid In Capital [Member] Additional paid-in capital [Member] Additions for credit losses not previously recognized. Additions For Credit Losses Not Previously Recognized Additions for credit losses not previously recognized Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Compensation expense, net Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities AFS investment securities - all other. Afs Investment Securities All Other [Abstract] AFS investment securities - all other: Allocated. Allocated [Member] Allocated [Member] All Other Segment. All Other [Member] All Other [Member] Amendment Flag Amendment Flag Amortization Of Intangible Assets Amortization of core deposit and other intangible assets Amortization Of Mortgage Servicing Rights M S Rs Amortization of capitalized servicing rights Amortization of preferred stock discount. Amortization Of Preferred Stock Discount Amortization of preferred stock discount Amortization of preferred stock discount. Amortizations Of Preferred Stock Discount Amortization of preferred stock discount (a) Amortized cost and estimated fair value of debt securities by contractual maturity. Amortized Cost And Estimated Fair Value Of Debt Securities By Contractual Maturity Table [Text Block] Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity Amortized cost and estimated fair value of investment securities. Amortized Cost And Estimated Fair Value Of Investment Securities Table [Text Block] Amortized Cost and Estimated Fair Value of Investment Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Antidilutive securities excluded from computation of earnings per share Asset Impairment Charges Asset write-downs Assets Total assets Assets [Abstract] Assets Assets Fair Value Disclosure Total assets Assets of subsidiaries providing reinsurance to satisfy claims. Assets Of Subsidiaries Providing Reinsurance To Satisfy Claims Assets of subsidiaries providing reinsurance to satisfy claims Assets taken in foreclosure of defaulted loans measured at fair value on a nonrecurring basis. Assets Taken In Foreclosure Of Defaulted Loans Measured At Fair Value On Nonrecurring Basis Nonrecurring fair value measurement Automobile Member. Automobile [Member] Automobile [Member] Available for sale ("AFS") investment securities with OTTI. Available For Sale Afs Investment Securities With Otti [Abstract] Available-for-sale ("AFS") investment securities with other- than- temporary impairment ("OTTI"): Available For Sale Securities Available for sale (cost: $5,091,116 at September 30, 2012; $6,312,423 at December 31, 2011) Estimated fair value Available For Sale Securities Amortized Cost Investment securities, available for sale, amortized cost Available For Sale Securities And Held To Maturity Securities [Table] Available For Sale Securities And Held To Maturity Securities [Table] Available For Sale Securities And Held To Maturity Securities [Table] Available For Sale Securities Change In Net Unrealized Holding Gain Loss Net unrealized gains (losses) on investment securities, before tax Available for sale securities continuous unrealized losses position less than 12 months aggregate losses. Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value Estimated fair value, Less than 12 months Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value Estimated fair value, 12 months or more Available for sale securities continuous unrealized loss position 12 months or more aggregate losses. Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost Due after five years through ten years Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value Due after five years through ten years Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost Due after one year through five years Available For Sale Securities Debt Maturities After One Through Five Years Fair Value Due after one year through five years Available For Sale Securities Debt Maturities After Ten Years Amortized Cost Due after ten years Available For Sale Securities Debt Maturities After Ten Years Fair Value Due after ten years Available For Sale Securities Debt Maturities Amortized Cost Total Available For Sale Securities Debt Maturities Amortized Cost [Abstract] Debt securities available for sale:b Available For Sale Securities Debt Maturities Fair Value [Abstract] Debt securities available for sale: b Available For Sale Securities Debt Maturities Within One Year Amortized Cost Due in one year or less Available For Sale Securities Debt Maturities Within One Year Fair Value Due in one year or less Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost Mortgage-backed securities available for sale Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value Mortgage-backed securities available for sale Available For Sale Securities Debt Maturities With Single Maturity Date Amortized Cost. Available For Sale Securities Debt Maturities With Single Maturity Date Amortized Cost Total available for sale (amortized cost) Available For Sale Securities Debt Maturities With Single Maturity Date Fair Value. Available For Sale Securities Debt Maturities With Single Maturity Date Fair Value Total available for available for sale (fair value) Available For Sale Securities Debt Securities Total Availableforsale Securities Gross Unrealized Gain Gross unrealized gains Available For Sale Securities Gross Unrealized Losses 1 Gross unrealized losses Average weighting placed on the values provided by the independent sources, in percentage. Average Weighting Placed On Values Provided By Independent Sources In Percentage Average weighting placed on the values provided by the independent sources, in percentage K Bank and Wilmington trust corporation acquisition. Bank Acquisition One And Wilmington Trust Corporation Acquisition [Member] K Bank and Wilmington Trust Corporation Acquisition [Member] Bayview And Colonial [Member] Bayview And Colonial [Member] Bayview and Colonial [Member] Brokerage Commissions Revenue Brokerage services income Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition Cost Of Acquired Entity Equity Interests Issued And Issuable Common shares issued (4,694,486 shares) Business Acquisition Cost Of Acquired Entity Number Of Shares Of Common Stock Issued Business Acquisition Cost Of Acquired Entity Number Of Shares Of Common Stock Issued Common shares issued Business acquisition Cost of acquired Entity preferred stock purchased. Business Acquisition Cost Of Acquired Entity Preferred Stock Purchased Preferred stock purchased from U.S. Treasury Business Acquisition Cost Of Acquired Entity Purchase Price Total purchase price Business Acquisition Equity Interest Issued Or Issuable Value Assigned Common shares issued for acquisition fair value Business Acquisition Equity Interests Issued Or Issuable Number Of Shares Issued Common stock issued for acquisition Business Acquisition [Line Items] Business Acquisition [Line Items] Business Acquisition Pro Forma Information [Text Block] Pro forma information Business Acquisition Purchase Price Allocation Amortizable Intangible Assets Core deposit and other intangibles Business Acquisition Purchase Price Allocation Assets Acquired Assets acquired total Total identifiable assets Business Acquisition Purchase Price Allocation Current Assets Cash And Cash Equivalents Cash and due from banks Business Acquisition Purchase Price Allocation Current Assets Marketable Securities Investment securities Business Acquisition Purchase Price Allocation Current Assets Receivables Loans and leases Business Acquisition Purchase Price Allocation Current Liabilities Accounts Payable Short-term borrowings Business acquisition purchase price allocation current liabilities deposits. Business Acquisition Purchase Price Allocation Current Liabilities Deposits Deposits Business Acquisition Purchase Price Allocation Liabilities Assumed Liabilities Total liabilities Business Acquisition Purchase Price Allocation Noncurrent Liabilities Long Term Debt Long-term borrowings Business acquisition purchase price allocation of Interest bearing deposits. Business Acquisition Purchase Price Allocation Of Interest Bearing Deposits Interest-bearing deposits at banks Business acquisition purchase price allocation of other short term investments. Business Acquisition Purchase Price Allocation Of Other Short Term Investments Other short-term investments Business Acquisition Purchase Price Allocation Other Noncurrent Assets Other assets Business Acquisition Purchase Price Allocation Other Noncurrent Liabilities Other liabilities Business Acquisitions Pro Forma Net Income Loss Net income pro forma Business Acquisitions Pro Forma Revenue Total revenues pro forma Business Banking Segment. Business Banking [Member] Business Banking [Member] Business Combination Disclosure [Text Block] Acquisitions Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles Core deposit and other intangibles Business Combination Separately Recognized Transactions Additional Disclosures Acquisition Cost Expensed Total merger-related expenses Liabilities. Business Combinations Liabilities [Abstract] Liabilities: Capitalized servicing assets for privately held company commercial mortgage loans. Capitalized Servicing Assets For Privately Held Company Commercial Mortgage Loans Amounts recorded as capitalized servicing assets for commercial mortgage loans Carrying Reported Amount Fair Value Disclosure [Member] Carrying amount [Member] Carrying value of loans in securitization trusts. Carrying Value Of Loans In Securitization Trusts Carrying value of loans in the securitization trusts Cash And Cash Equivalents At Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Net increase in cash and cash equivalents Cash And Due From Banks Cash and due from banks Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Supplemental schedule of noncash investing and financing activities Cash [Member] Cash [Member] Certain loans acquired in transfer accounted for As debt securities accretable yield accretion. Certain Loans Acquired In Transfer Accounted For As Debt Securities Accretable Yield Accretion Table [Text Block] Summary of Changes in Accretable Yield for Acquired Loans Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Balance at end of period Balance at beginning of period Accretable yield balance Certain loans acquired in transfer not accounted for as debt securities accretable yield interest income. Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Interest Income Interest income Interest income Certain loans acquired in transfer not accounted for as debt securities accretable yield interest other increase decrease. Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Interest Other Increase Decrease Other Certain loans acquired in transfer not accounted for as debt securities accretable yield reclassifications from to non-accretable difference net. Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications From To Non Accretable Difference Net Reclassifications from (to) nonaccretable balance, net Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Acquired During Period At Acquisition At Fair Value Contractual principal and interest payments Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net Purchased impaired Change in fair value of nonrecurring fair value measured foreclosed assets. Change In Fair Value Of Nonrecurring Fair Value Measured Foreclosed Assets Changes in fair value recognized for those foreclosed assets held Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves. Change In Fair Value Of Nonrecurring Fair Value Measured Loans For Charge Offs And Impairment Reserves Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves Change In Unrealized Gain Loss On Fair Value Hedging Instruments Derivatives in fair value hedging relationships, derivatives Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge Derivatives in fair value hedging relationships, hedged item The tabular disclosure of changes in allowance for credit losses. Changes In Allowance For Credit Losses Table [Text Block] Changes in Allowance for Credit Losses Changes in credit losses associated with debt securities for which other-than-temporary impairment losses. Changes In Credit Losses Associated With Debt Securities For Which Other Than Temporary Impairment Losses Table [Text Block] Changes in Credit Losses Associated with Debt Securities for Which Other-Than-Temporary Impairment Losses The tabular disclosure of changes in level 3 assets and liabilities measured at estimated fair value on recurring basis. Changes In Level Three Assets And Liabilities Measured At Estimated Fair Value On Recurring Basis Table [Text Block] Changes in Level 3 Assets and Liabilities Measured at Estimated Fair Value on a Recurring Basis Class Of Financing Receivable [Member] Impaired financing receivable with no related allowance [Member] Class Of Stock [Domain] Class of Stock [Domain] Class Of Stock [Line Items] Class of Stock [Line Items] Class Of Warrant Or Right Exercise Price Of Warrants Or Rights Exercise price of each class of warrants or rights outstanding Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Ten-year warrant to purchase common stock Collateral Already Posted Aggregate Fair Value Fair value of collateral already posted for derivative financial instruments Collateral Already Posted Aggregate Fair Value Derivative Instruments In Net Liability Position Collateral Already Posted Aggregate Fair Value Derivative Instruments In Net Liability Position Collateral already posted aggregate fair value derivative instruments in net liability position Collateralized Debt Obligations [Member] Collateralized debt obligations [Member] Collectively evaluated for impairment. Collectively Evaluated For Impairment [Member] Collectively evaluated for impairment [Member] Combination of concession types. Combination Of Concession Types [Member] Combination of concession types [Member] Combined Outstanding Principal Amount Of Mortgage Backed Securities Issued By Qualified Special Purpose Trusts Held By Unrelated Parties Combined Outstanding Principal Amount Of Mortgage Backed Securities Issued By Qualified Special Purpose Trusts Held By Unrelated Parties Combined outstanding principal amount of mortgage backed securities issued by qualified special purpose trusts held by unrelated parties Commercial Banking Segment. Commercial Banking [Member] Commercial Banking [Member] Commercial financial leasing. Commercial Financial Leasing [Member] Commercial, financial, leasing, etc [Member] Commercial mortgage loans of privately held company. Commercial Mortgage Loans Of Privately Held Company Outstanding principal balances of commercial mortgage servicing rights obtained from Bayview Financial Commercial real estate excluding residential builder and developer and other construction. Commercial Real Estate Excluding Residential Builder And Developer And Other Construction [Member] Commercial [Member] Commercial Real Estate [Member] Commercial real estate loans [Member] Commercial Real Estate Portfolio Segment [Member] Real Estate Commercial [Member] Commercial Real Estate Segment. Commercial Real Estate Segment [Member] Commercial Real Estate [Member] Commitments And Contingencies Disclosure [Text Block] Commitments and contingencies Commitments regarding Commercial letters of credit. Commitments Regarding Commercial Letters Of Credit Commercial letters of credit Commitments regarding Financial guarantees and indemnification contracts. Commitments Regarding Financial Guarantees And Indemnification Contracts Financial guarantees and indemnification contracts Commitments regarding Standby letters of credit. Commitments Regarding Standby Letters Of Credit Standby letters of credit The tabular disclosure of commitments. Commitments Table [Text Block] Company's Significant Commitments Commitments to Extend Credit. Commitments To Extend Credit [Abstract] Commitments to extend credit Commitments to extend credit for Commercial and other. Commitments To Extend Credit For Commercial And Other Commercial and other Commitments to extend credit for Commercial real estate loans to be sold. Commitments To Extend Credit For Commercial Real Estate Loans To Be Sold Commercial real estate loans to be sold Commitments to extend credit for Home equity lines of credit. Commitments To Extend Credit For Home Equity Lines Of Credit Home equity lines of credit Commitments to extend credit for Other commercial real estate and construction. Commitments To Extend Credit For Other Commercial Real Estate And Construction Other commercial real estate and construction Commitments to extend credit for Other residential real estate. Commitments To Extend Credit For Other Residential Real Estate Other residential real estate Commitments to extend credit for Residential real estate loans to be sold. Commitments To Extend Credit For Residential Real Estate Loans To Be Sold Residential real estate loans to be sold Commitments to originate real estate loans for sale. Commitments To Originate Real Estate Loans For Sale Commitments to originate real estate loans for sale Commitments to originate real estate loans. Commitments To Originate Real Estate Loans [Member] Commitments to originate real estate loans [Member] Commitments to sell real estate loans. Commitments To Sell Real Estate Loans [Member] Commitments to sell real estate loans [Member] Commitments To Sell Real Estate Loans Notional Amount. Commitments To Sell Real Estate Loans Notional Amount Commitments to sell real estate loans Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards. Common Shares Outstanding Including Common Stock Issuable And Unvested Stock Based Compensation Awards Common and unvested stock-based compensation awards Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards Common Stock Dividends Per Share Cash Paid Cash dividends per common share Common Stock Dividends Per Share Declared Common stock per share dividend amount The obligation to issue shares of Company common stock in connection with deferred compensation plans. Common Stock Issuable Common stock issuable, 57,316 shares at September 30, 2012; 68,220 shares at December 31, 2011 Common stock issuable. Common Stock Issuable [Member] Common stock issuable [Member] Number of shares of common stock issuable in connection with deferred Compensation plans. Common Stock Issuable Shares Common stock issuable, shares Common Stock [Member] Common stock [Member] Common Stock Par Or Stated Value Per Share Common stock, par value Common Stock Shares Authorized Common stock, shares authorized Common Stock Shares Issued Common stock, shares issued Common Stock Value Common stock, $.50 par, 250,000,000 shares authorized, 127,403,420 shares issued at September 30, 2012; 125,683,398 shares issued at December 31, 2011 The tabular disclosure of components of other comprehensive income loss. Components Of Other Comprehensive Income Loss Table [Text Block] Components of Other Comprehensive Income Comprehensive Income Note [Text Block] Comprehensive income Consolidation Policy [Text Block] Consolidation Consumer Loan [Member] Consumer loans [Member] Consumer Loans Auto Financing Receivable [Member] Automobile [Member] Consumer Other Financing Receivable [Member] Other [Member] Consumer Portfolio Segment [Member] Consumer [Member] Conversion of convertible securities during period value. Conversion Of Convertible Securities During Period Value Conversion of Series B preferred stock into 433,144 shares of common stock Conversion Of Stock Amount Issued 1 Common stock issued Credit Derivatives By Contract Type [Axis] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Credit Derivatives [Line Items] Credit Derivatives [Line Items] Credit risk derivative. Credit Risk Derivative [Member] Credit Risk Derivative [Member] Criticized accrual. Criticized Accrual [Member] Criticized Accrual [Member] Criticized nonaccrual. Criticized Nonaccrual [Member] Criticized Nonaccrual [Member] Current Fiscal Year End Date Current Fiscal Year End Date Debt Disclosure [Text Block] Borrowings Debt Instrument Maturity Date Junior Subordinated Debentures Maturity Date Debt Instrument Maturity Date Range End 1 Debt Maturity, End Year Debt Instrument Maturity Date Range Start 1 Debt Maturity, Start Year Debt instrument weighted average basis spread on variable rate. Debt Instrument Weighted Average Basis Spread On Variable Rate Debt instrument weighted average basis spread on variable rate Debt Security [Axis] Debt Security [Axis] Deferred Income Tax Expense Benefit Provision for deferred income taxes Defined Benefit Plan Actuarial Gain Loss Amortization of net actuarial loss Defined Benefit Plan Amortization Of Prior Service Cost Credit Amortization of prior service cost