The amount of cash balances required to meet regulatory reserve requirements of the Federal Reserve Board.

No definition available.

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

- Definition

The amount of cumulative days past due that would generally trigger charge offs for retail consumer loans not adequately secured.

+ References

No definition available.

+ Details

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Namespace Prefix:	mrbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of mortgage loan production offices.

+ References

No definition available.

+ Details

Name:	mrbk_NumberOfMortgageLoanProductionOffices
Namespace Prefix:	mrbk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The general amount of time between the issuance of a loan commitment and closing and sale of the loan.

+ References

No definition available.

+ Details

Name:	mrbk_TimeElapsingBetweenLoanCommitmentAndSaleOfLoan
Namespace Prefix:	mrbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Carrying amount of other real estate not separately disclosed, including, but not limited to, real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. This does not include real estate assets taken in settlement of troubled loans through surrender or foreclosure.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Summary of Significant Accounting Policies - Cash Flows, Allowance for Loan Losses and Mortgage Banking Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) Office	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)
Presentation of Cash Flows
Cash balances	$ 1,500	$ 1,500	$ 1,500
Allowance for Loan Losses
Cumulative days past due for charge off for retail consumer loans	120 days
Mortgage Banking Activities and Mortgage Loans Held for Sale
Number of mortgage loan production offices		13	13
Other real estate owned
Other real estate owned	$ 0	$ 0	$ 0	$ 437
Minimum
Mortgage Banking Activities and Mortgage Loans Held for Sale
Loan commitment to sale duration	30 days
Maximum
Mortgage Banking Activities and Mortgage Loans Held for Sale
Loan commitment to sale duration	120 days