Loans And The Allowance For Credit Losses (Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Loans And The Allowance For Credit Losses [Abstract]
Nonaccrual loans	$ 2,876	$ 2,355
Loans greater than 90 days and accruing	0	0
TDRs	539	557
Total nonperforming loans	$ 3,415	$ 2,912

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

No definition available.

+ Details

Name:	mbvt_ImpairedFinancingReceivableRecordedInvestments
Namespace Prefix:	mbvt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Nonaccrual non-troubled debt restructured loans.

+ References

No definition available.

+ Details

Name:	mbvt_NonaccrualNonTroubledDebtRestructuredLoans
Namespace Prefix:	mbvt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5111-111524

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant