REVENUE RECOGNITION (Details)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Maximum
Percentage of all services charges on deposit accounts to total revenue	1.40%	1.40%

The percentage of all services charges on deposit accounts to total revenue

No definition available.

Name:	mcbs_PercentageOfServiceChargesOnDepositAccountsToTotalRevenue
Namespace Prefix:	mcbs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration