Line of credit facility, additional borrowing capacity.

No definition available.

Name:	mtb_LineOfCreditFacilityAdditionalBorrowingCapacity
Namespace Prefix:	mtb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Description of reference rate used for variable rate of debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

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+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Latest date the outstanding debt instruments are required to be repaid, in YYYY-MM-DD format.

+ References

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Period Type:	duration

- Definition

Earliest date the outstanding debt instruments are required to be repaid, in YYYY-MM-DD format.

+ References

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Borrowings - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Junior subordinated debentures		$ 537,000
Debt Maturity, Start Year		Jan. 01, 2027
Debt Maturity, End Year		Dec. 31, 2033
Description of variable rate basis	Secured Overnight Financing Rate ("SOFR")
Short-term borrowings		$ 6,995,302	$ 3,554,951
Additional borrowing capacity		17,100,000
Available line of credit		15,400,000
Long-term borrowings		$ 7,462,890	$ 3,964,537
5.053% Fixed Rate Senior Notes Due to Mature in January 2034 [Member]
Debt Instrument [Line Items]
Senior notes	$ 1,000,000
Senior notes maturity date	Jan. 31, 2034
Interest rate of debt instrument	5.053%
Variable interest rate of debt instrument	1.85%
4.65% Fixed Rate Senior Notes Due to Mature in January 2026 [Member]
Debt Instrument [Line Items]
Senior notes	$ 1,300,000
Senior notes maturity date	Jan. 31, 2026
Interest rate of debt instrument	4.65%
4.70% Fixed Rate Senior Notes Due to Mature in January 2028 [Member]
Debt Instrument [Line Items]
Senior notes	$ 1,200,000
Senior notes maturity date	Jan. 31, 2028
Interest rate of debt instrument	4.70%