Loans And The Allowance For Credit Losses (Loan Loss Experience And Activity In The Allowance For Credit Losses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 12,828	$ 12,312	$ 11,353
Charge-offs	(231)	(412)	(61)
Recoveries	68	128	70
Provision (credit)	150	800	950
Ending balance	12,815	12,828	12,312
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
Loans	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
Commercial, Financial And Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	3,354	3,447	2,905
Charge-offs	(34)	(20)	(9)
Recoveries	10	62	30
Provision (credit)	1	(135)	521
Ending balance	3,331	3,354	3,447
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
Loans	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
Municipal Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	768	522	309
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (credit)	(132)	246	213
Ending balance	636	768	522
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
Loans	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
Real Estate Loans – Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	3,081	3,421	3,017
Charge-offs	(25)	(289)	(20)
Recoveries	24	6	14
Provision (credit)	47	(57)	410
Ending balance	3,127	3,081	3,421
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
Loans	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
Real Estate Loans – Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,085	4,660	4,605
Charge-offs	0	(1)	(32)
Recoveries	1	40	1
Provision (credit)	165	386	86
Ending balance	5,251	5,085	4,660
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
Loans	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
Real Estate Loans – Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	512	234	477
Charge-offs	0	0	0
Recoveries	0	1	25
Provision (credit)	(97)	277	(268)
Ending balance	415	512	234
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
Loans	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
Installment Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	18	17	23
Charge-offs	(2)	(9)	0
Recoveries	2	6	0
Provision (credit)	(5)	4	(6)
Ending balance	13	18	17
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
Loans	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
All Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	10	11	17
Charge-offs	(170)	(93)	0
Recoveries	31	13	0
Provision (credit)	171	79	(6)
Ending balance	42	10	11
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
Loans	33	895
Allowance for loan losses	42	10
Reserve for undisbursed lines of credit	0	0
Total allowance for credit losses	$ 42	$ 10	$ 11

Reserve for undisbursed lines of credit

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- Definition

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

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

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

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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

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

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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.

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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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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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