Loans And The Allowance For Credit Losses (Allowance For Loan Losses And The Recorded Investment In Loans) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	$ 63	$ 112
Ending balance collectively evaluated for impairment	12,752	12,716
Financing receivables, Ending balance individually evaluated for impairment	791	906
Financing receivables, Ending balance collectively evaluated for impairment	1,181,543	1,165,327
Total	1,182,334	1,166,233
Allowance for loan losses	11,833	12,042
Reserve for undisbursed lines of credit	982mbvt_ReserveForUndisbursedLinesOfCredit	786mbvt_ReserveForUndisbursedLinesOfCredit
Total allowance for credit losses	12,815	12,828	12,312	11,353
Commercial, Financial And Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	2
Ending balance collectively evaluated for impairment	3,331	3,352
Financing receivables, Ending balance individually evaluated for impairment	134	20
Financing receivables, Ending balance collectively evaluated for impairment	177,463	172,790
Total	177,597	172,810
Allowance for loan losses	2,583	2,740
Reserve for undisbursed lines of credit	748	614
Total allowance for credit losses	3,331	3,354	3,447	2,905
Municipal Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	636	768
Financing receivables, Ending balance individually evaluated for impairment	0	0
Financing receivables, Ending balance collectively evaluated for impairment	94,366	94,007
Total	94,366	94,007
Allowance for loan losses	623	758
Reserve for undisbursed lines of credit	13	10
Total allowance for credit losses	636	768	522	309
Real Estate Loans – Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	63	41
Ending balance collectively evaluated for impairment	3,064	3,040
Financing receivables, Ending balance individually evaluated for impairment	657	722
Financing receivables, Ending balance collectively evaluated for impairment	468,872	488,984
Total	469,529	489,706
Allowance for loan losses	3,038	2,995
Reserve for undisbursed lines of credit	89	86
Total allowance for credit losses	3,127	3,081	3,421	3,017
Real Estate Loans – Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	69
Ending balance collectively evaluated for impairment	5,251	5,016
Financing receivables, Ending balance individually evaluated for impairment	0	164
Financing receivables, Ending balance collectively evaluated for impairment	412,447	371,155
Total	412,447	371,319
Allowance for loan losses	5,209	5,040
Reserve for undisbursed lines of credit	42	45
Total allowance for credit losses	5,251	5,085	4,660	4,605
Real Estate Loans – Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	415	512
Financing receivables, Ending balance individually evaluated for impairment	0	0
Financing receivables, Ending balance collectively evaluated for impairment	23,858	31,841
Total	23,858	31,841
Allowance for loan losses	325	481
Reserve for undisbursed lines of credit	90	31
Total allowance for credit losses	415	512	234	477
Installment Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	13	18
Financing receivables, Ending balance individually evaluated for impairment	0	0
Financing receivables, Ending balance collectively evaluated for impairment	4,504	5,655
Total	4,504	5,655
Allowance for loan losses	13	18
Reserve for undisbursed lines of credit	0	0
Total allowance for credit losses	13	18	17	23
All Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending balance individually evaluated for impairment	0	0
Ending balance collectively evaluated for impairment	42	10
Financing receivables, Ending balance individually evaluated for impairment	0	0
Financing receivables, Ending balance collectively evaluated for impairment	33	895
Total	33	895
Allowance for loan losses	42	10
Reserve for undisbursed lines of credit	0	0
Total allowance for credit losses	$ 42	$ 10	$ 11	$ 17

Reserve for undisbursed lines of credit

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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(1)

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

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-Paragraph 11B

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (h)

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (h)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

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-Name Accounting Standards Codification

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-Paragraph 2

-Subparagraph (b)(1)(ii)

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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