XML 58 R39.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Loans and Allowance for Loan Losses - Nonperforming Loans (Detail) (USD $) | Sep. 30, 2013 | Dec. 31, 2012
--- | --- | ---
Receivables [Abstract] |  |
Loans past due 90 days or more still accruing interest | $ 0 | $ 0
Nonaccrual loans | 10,526,000 | 18,970,000
Total nonperforming loans | $ 10,526,000 | $ 18,970,000

X
- Definition Financing receivable past due ninety days or more and still accruing interest and nonaccrual loans and troubled debt restructurings accruing interest net. + References No definition available. + Details
Name: | mbwm_FinancingReceivablePastDueNinetyDaysOrMoreAndStillAccruingInterestAndNonaccrualLoansAndTroubledDebtRestructuringsAccruingInterestNet
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Recorded investment in financing receivables that are 90 days or more past due and still accruing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration