XML 51 R41.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Note 3 - Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans (Details) - USD ($) | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Loans | $ 2,636,856,000 | $ 2,558,552,000
Originated Loan [Member] |  |
Past due loans | 464,000 | 2,451,000
Current loans | 2,295,740,000 | 2,167,506,000
Loans | 2,296,204,000 | 2,169,957,000
Loans past due 90 days or more still accruing interest | 0 | 0
Acquired Loan [Member] |  |
Past due loans | 2,211,000 | 3,479,000
Current loans | 338,441,000 | 385,116,000
Loans | 340,652,000 | 388,595,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] |  |
Loans | 2,261,970,000 | 2,203,568,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] |  |
Loans | 776,995,000 | 753,764,000
Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Loans | 37,868,000 | 29,873,000
Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member] |  |
Loans | 533,075,000 | 526,328,000
Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Loans | 818,376,000 | 791,685,000
Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Loans | 95,656,000 | 101,918,000
Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 195,000 | 1,457,000
Current loans | 2,026,998,000 | 1,932,771,000
Loans | 2,027,193,000 | 1,934,228,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Originated Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 178,000
Current loans | 712,138,000 | 680,627,000
Loans | 712,138,000 | 680,805,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Originated Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 35,000
Current loans | 32,031,000 | 23,647,000
Loans | 32,031,000 | 23,682,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 195,000 | 1,244,000
Current loans | 477,501,000 | 454,821,000
Loans | 477,696,000 | 456,065,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Current loans | 743,102,000 | 708,824,000
Loans | 743,102,000 | 708,824,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Current loans | 62,226,000 | 64,852,000
Loans | 62,226,000 | 64,852,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 365,000 | 1,181,000
Current loans | 234,412,000 | 268,159,000
Loans | 234,777,000 | 269,340,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 154,000
Current loans | 64,857,000 | 72,805,000
Loans | 64,857,000 | 72,959,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 18,000 | 14,000
Current loans | 5,819,000 | 6,177,000
Loans | 5,837,000 | 6,191,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 339,000 | 905,000
Current loans | 55,040,000 | 69,358,000
Loans | 55,379,000 | 70,263,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Current loans | 75,274,000 | 82,861,000
Loans | 75,274,000 | 82,861,000
Loans past due 90 days or more still accruing interest | 0 | 0
Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 8,000 | 108,000
Current loans | 33,422,000 | 36,958,000
Loans | 33,430,000 | 37,066,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] |  |
Loans | 374,886,000 | 354,984,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member] |  |
Loans | 91,229,000 | 100,425,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] |  |
Loans | 283,657,000 | 254,559,000
Retail Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 269,000 | 994,000
Current loans | 268,742,000 | 234,735,000
Loans | 269,011,000 | 235,729,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] | Originated Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 46,000 | 744,000
Current loans | 66,637,000 | 68,931,000
Loans | 66,683,000 | 69,675,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] | Originated Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 223,000 | 250,000
Current loans | 202,105,000 | 165,804,000
Loans | 202,328,000 | 166,054,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 1,846,000 | 2,298,000
Current loans | 104,029,000 | 116,957,000
Loans | 105,875,000 | 119,255,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] | Acquired Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 384,000 | 614,000
Current loans | 24,162,000 | 30,136,000
Loans | 24,546,000 | 30,750,000
Loans past due 90 days or more still accruing interest | 0 | 0
Retail Portfolio Segment [Member] | Acquired Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 1,462,000 | 1,684,000
Current loans | 79,867,000 | 86,821,000
Loans | 81,329,000 | 88,505,000
Loans past due 90 days or more still accruing interest | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Originated Loan [Member] |  |
Past due loans | 46,000 | 647,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Acquired Loan [Member] |  |
Past due loans | 937,000 | 1,786,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 18,000 | 688,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 40,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 18,000 | 14,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 0 | 634,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 46,000 | 647,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 46,000 | 647,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 919,000 | 1,098,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 219,000 | 408,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 700,000 | 690,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Originated Loan [Member] |  |
Past due loans | 51,000 | 11,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Acquired Loan [Member] |  |
Past due loans | 676,000 | 385,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 96,000 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 96,000 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 51,000 | 11,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 0 | 11,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 51,000 | 0
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 580,000 | 385,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 70,000 | 52,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 510,000 | 333,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Originated Loan [Member] |  |
Past due loans | 367,000 | 1,793,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Acquired Loan [Member] |  |
Past due loans | 598,000 | 1,308,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 195,000 | 1,457,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 178,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 35,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 195,000 | 1,244,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Originated Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 251,000 | 493,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Commercial and Industrial [Member] |  |
Past due loans | 0 | 114,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Vacant Land and Land Development and Residential Construction Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Owner Occupied Loan [Member] |  |
Past due loans | 243,000 | 271,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Non Owner Occupied Loan [Member] |  |
Past due loans | 0 | 0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Acquired Loan [Member] | Real Estate Multi Family and Residential Rental Loan [Member] |  |
Past due loans | 8,000 | 108,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] |  |
Past due loans | 172,000 | 336,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 0 | 86,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Originated Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | 172,000 | 250,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] |  |
Past due loans | 347,000 | 815,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | Home Equity and Other [Member] |  |
Past due loans | 95,000 | 154,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Retail Portfolio Segment [Member] | Acquired Loan [Member] | One to Four Family Mortgages [Member] |  |
Past due loans | $ 252,000 | $ 661,000

X
- Definition Recorded investment in financing receivables that are 90 days or more past due and still accruing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Financing receivables that are current. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Recorded Investment in financing receivables that are past due at the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentPastDue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_VacantLandAndLandDevelopmentAndResidentialConstructionLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateOwnerOccupiedLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateNonOwnerOccupiedLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_RealEstateMultiFamilyAndResidentialRentalLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_HomeEquityAndOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables60To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |