Commitments And Contingencies (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Commitments And Contingencies [Abstract]
Contingent obligations under standby letters of credit	$ 4.68
Expiration term of contingent obligations, months	12 months

Contingent Obligations Under Standby Letters Of Credit

No definition available.

Name:	mbvt_ContingentObligationsUnderStandbyLettersOfCredit
Namespace Prefix:	mbvt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration