Name:	mbwm_AmortizationPeriodForTermDebtSecuredByRealEstate
Namespace Prefix:	mbwm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of federal reserve requirement at period end that can be met with vault cash or deposits at a Federal Reserve Bank.

No definition available.

Name:	mbwm_AmountOfFederalReserveRequired
Namespace Prefix:	mbwm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Period of time between issuance and maturity of interest rate swap agreements, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	mbwm_FeesAccretedIntoIncomeDuringInterestRateSwapAgreementsTerm
Namespace Prefix:	mbwm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Stated interest rates on loans that are secured by non-real estate collateral.

No definition available.

Name:	mbwm_InterestRatesOnLoansSecuredByNonRealEstateCollateral
Namespace Prefix:	mbwm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The carrying amount for the reserve or liability for financial instruments with off-balance sheet risk.

No definition available.

Name:	mbwm_ReserveOrLiabilityBalanceForFinancialInstrumentsWithOffBalanceSheetRisk
Namespace Prefix:	mbwm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Period of time between issuance and maturity of term debt secured by non-real estate collateral, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	mbwm_TermDebtSecuredByNonRealEstateCollateralMaturityPeriod
Namespace Prefix:	mbwm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The period in which term debt becomes secured by a balloon payment.

No definition available.

Name:	mbwm_TermDebtSecuredByRealEstateBalloonPaymentPeriod
Namespace Prefix:	mbwm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674