Acquisitions (Details 2) (Wilmington Trust Corporation [Member], USD $) In Thousands	1 Months Ended
May 31, 2011	May 16, 2011
Wilmington Trust Corporation [Member]
Purchase price:
Value of common shares issued		$ 405,557
Preferred stock purchased from U.S. Treasury		330,000
Total purchase price		735,557
Identifiable assets:
Cash and due from banks		178,940
Interest-bearing deposits at banks		2,606,265
Other short-term investments		57,817
Investment securities		510,390
Loans and leases		6,410,430
Core deposit and other intangibles		176,194
Other assets		905,006
Total identifiable assets		10,845,042
Liabilities:
Deposits		8,864,161
Short-term borrowings		147,752
Long-term borrowings		600,830
Other liabilities		431,812
Total liabilities		10,044,555
Net gain resulting from acquisition	$ 64,930

Business acquisition Cost of acquired Entity preferred stock purchased.

Name:	mtb_BusinessAcquisitionCostOfAcquiredEntityPreferredStockPurchased
Namespace Prefix:	mtb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Business acquisition purchase price allocation current liabilities deposits.

+ Details

Name:	mtb_BusinessAcquisitionPurchasePriceAllocationCurrentLiabilitiesDeposits
Namespace Prefix:	mtb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Business acquisition purchase price allocation of Interest bearing deposits.

+ Details

Name:	mtb_BusinessAcquisitionPurchasePriceAllocationOfInterestBearingDeposits
Namespace Prefix:	mtb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Business acquisition purchase price allocation of other short term investments.

+ Details

Name:	mtb_BusinessAcquisitionPurchasePriceAllocationOfOtherShortTermInvestments
Namespace Prefix:	mtb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Liabilities.

+ Details

Name:	mtb_BusinessCombinationsLiabilitiesAbstract
Namespace Prefix:	mtb
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Identifiable assets.

+ Details

Name:	mtb_IdentifiableAssetsAbstract
Namespace Prefix:	mtb
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Purchase price.

+ Details

Name:	mtb_PurchasePriceAbstract
Namespace Prefix:	mtb
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The acquisition-date fair value of the equity interests of the acquirer, including the number of instruments or interests issued or issuable in consideration for the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 68
-Subparagraph f(4)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 88-16

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph d

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 39

+ Details

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityEquityInterestsIssuedAndIssuable
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph d

+ Details

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityPurchasePrice
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will be amortized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 52

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationAmortizableIntangibleAssets
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to assets acquired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 37
-Subparagraph g

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationAssetsAcquired
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of cash and cash equivalents acquired in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentAssetsCashAndCashEquivalents
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to marketable securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 37
-Subparagraph a

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentAssetsMarketableSecurities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to receivables.

+ References

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentAssetsReceivables
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to accounts payable of the acquired entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentLiabilitiesAccountsPayable
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to liabilities assumed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 37
-Subparagraph g

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 98-1

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationLiabilitiesAssumed
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to the noncurrent portion of the long-term debt assumed from the acquired entity.

+ References

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationNoncurrentLiabilitiesLongTermDebt
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to noncurrent assets of the acquired entity, except for property plant and equipment, intangible assets, and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 98-1

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 37
-Subparagraph f

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationOtherNoncurrentAssets
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to other noncurrent liabilities of the acquired entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph e

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationOtherNoncurrentLiabilities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the excess of the fair value of acquired net assets over the cost of an acquired business after pro rata reduction of the amounts that otherwise would have been assigned to acquired assets except financial assets other than investments accounted for by the equity method, assets to be disposed of by sale, deferred tax assets, prepaid assets relating to pension and postretirement benefit plans, and other current assets. This amount is considered an extraordinary item and often referred to as negative goodwill. This element is gross of the related tax effect.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 44, 45, 46

+ Details

Name:	us-gaap_GainOnPurchaseOfBusiness
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration