XML 69 R59.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Note 8 - Commitments and Off-Balance Sheet Risk - Exposure to Credit Losses (Details) - USD ($) | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Contractual amounts of financial instruments with off-balance sheet risk | $ 1,028,671,000 | $ 1,012,197,000
Standby Letters of Credit [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | 22,433,000 | 26,030,000
Unused lines of Credit [Member] | Commercial Portfolio Segment [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | 730,070,000 | 682,202,000
Unused lines of Credit [Member] | One to Four Family Mortgages [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | 57,680,000 | 61,606,000
Unused lines of Credit [Member] | Consumer Portfolio Segment [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | 45,821,000 | 39,807,000
Unused lines of Credit [Member] | Consumer Other Financing Receivable 1 [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | 20,972,000 | 17,629,000
Loan Origination Commitments [Member] |  |
Contractual amounts of financial instruments with off-balance sheet risk | $ 151,695,000 | $ 184,923,000

X
- Definition The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611 + Details
Name: | us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_CreditFacilityAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_UnusedLinesOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=mbwm_OneToFourFamilyMortgagesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=mbwm_ConsumerOtherFinancingReceivable1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_LoanOriginationCommitmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |