Allowance for Loan Losses (the Allowance) - Carrying value based on performance status (Details) $ in Thousands	Mar. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Loans and Leases by Credit Ratings
Troubled debt restructurings	$ 3,762	$ 3,918
Evaluated by performance status
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	43,230	44,819
Performing
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	39,426	43,965
Nonperforming
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	3,804	854
Residential mortgage \| Evaluated by performance status
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	42,101	43,119
Residential mortgage \| Performing
Loans and Leases by Credit Ratings
Troubled debt restructurings	0	0
Carrying value of residential mortgage, consumer and leases	38,297	42,265
Residential mortgage \| Nonperforming
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	$ 3,804	$ 854
Number of loans \| loan	5	5
Loans receivable, net of the allowance and lease losses	$ 890	$ 839
Consumer \| Evaluated by performance status
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	570	1,003
Consumer \| Performing
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	570	1,003
Leases \| Evaluated by performance status
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	559	697
Leases \| Performing
Loans and Leases by Credit Ratings
Carrying value of residential mortgage, consumer and leases	$ 559	$ 697

The balance of financing receivables for residential mortgage, consumer and leases.

No definition available.

Name:	mrbk_FinancingReceivableForResidentialMortgageConsumerAndLeases
Namespace Prefix:	mrbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of loans.

+ References

No definition available.

+ Details

Name:	mrbk_NumberOfLoans
Namespace Prefix:	mrbk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

Name:	us-gaap_LoansReceivableFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=mrbk_FinancialInstrumentsEvaluatedByPerformanceStatusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=mrbk_LeasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: