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Note 12 - Related Parties (Details Textual) - USD ($) | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Related Party Deposits and Repurchase Agreements | $ 18,400,000 | $ 19,400,000 |
Directors and Executive Officers [Member] |  |  |
Loan Commitments to Related Parties | 104,000,000 | 122,000,000 |
Loans and Leases Receivable, Related Parties, Ending Balance | 87,672,000 | 108,042,000 | $ 104,043,000
Directors [Member] | SBA, CARES Act, Paycheck Protection Program [Member] |  |  |
Loans and Leases Receivable, Related Parties, Ending Balance | $ 0 | $ 300,000 |

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- Definition Represents the amount of loan commitments to related parties of the Company. + References No definition available. + Details
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Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Represents the balances of related party deposits and repurchase agreements. + References No definition available. + Details
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Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(e)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
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- Details
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Namespace Prefix: |
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- Details
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- Details
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Data Type: | na
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