Note 2 - Revenue Recognition (Details Textual)	3 Months Ended
Mar. 31, 2018
Revenue from Interest Income and Noninterest Income, Percent	93.40%

Represents the percentage of revenue from interest income and noninterest income.

No definition available.

Name:	mbcn_RevenueFromInterestIncomeAndNoninterestIncomePercent
Namespace Prefix:	mbcn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration