XML 54 R44.htm IDEA: XBRL DOCUMENT
v3.25.2

Note 3 - Loans and Allowance for Credit Losses (Details Textual) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2025 | Jun. 30, 2025 USD ($) | Jun. 30, 2024 USD ($) | Dec. 31, 2024 USD ($)
Financing Receivable, before Allowance for Credit Loss |  | $ 4,698,019 |  | $ 4,600,781
Increase (Decrease) in Finance Receivables |  | $ 97,200 |  |
Loans and Leases Receivable, Percentage Period Increase (Decrease) |  | 2.10% |  |
Financing Receivable, Nonaccrual, Interest Income |  | $ 300 | $ 400 |
Financing Receivable, Revolving, Converted to Term Loan During Period |  | 600 |  | 9,100
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease) From Forecast Changes |  | (100) |  | (2,200)
Financing Receivable, Individually Evaluated for Credit Loss |  | 11,200 |  | 7,400
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment |  | 3,900 |  | 2,200
Financing Receivable, Modifications, Number of Contracts | 0 |  |  |
Commercial Portfolio Segment [Member] |  |  |  |
Financing Receivable, before Allowance for Credit Loss |  | $ 3,821,158 |  | $ 3,707,304
Financing Receivables, Prepayment Speed Assumed |  | 2.00% |  | 2.00%
Retail Portfolio Segment [Member] |  |  |  |
Financing Receivable, before Allowance for Credit Loss |  | $ 876,861 |  | $ 893,477
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] |  |  |  |
Financing Receivable, before Allowance for Credit Loss |  | $ 799,427 |  | $ 827,597
Financing Receivables, Prepayment Speed Assumed |  | 7.80% |  | 7.80%
Retail Portfolio Segment [Member] | Other Consumer Loans [Member] |  |  |  |
Financing Receivable, before Allowance for Credit Loss |  | $ 77,434 |  | $ 65,880
Financing Receivables, Prepayment Speed Assumed |  | 7.80% |  | 7.80%

X
- Definition Amount of increase (decrease) in allowance for credit loss on financing receivable due economic forecast changes. + References No definition available. + Details
Name: | mbwm_FinancingReceivableAllowanceForCreditLossPeriodIncreaseDecreaseFromForecastChanges
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References No definition available. + Details
Name: | mbwm_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment
Namespace Prefix: | mbwm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of financing receivables that have been modified by troubled debt restructurings. + References No definition available. + Details
Name: | mbwm_FinancingReceivableModificationsNumberOfContracts
Namespace Prefix: | mbwm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of prepayment speed assumed under financing receivables. + References No definition available. + Details
Name: | mbwm_FinancingReceivablesPrepaymentSpeedAssumed
Namespace Prefix: | mbwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The percentage of increase or (decrease) during the period in loans and leases receivable during the period. + References No definition available. + Details
Name: | mbwm_LoansAndLeasesReceivablePercentagePeriodIncreaseDecrease
Namespace Prefix: | mbwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of financing receivable individually evaluated for credit loss. Excludes financing receivable collectively evaluated for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.5.a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480418/310-10-S99-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11C -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-11C + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of interest income on financing receivable on nonaccrual status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase in term loan from conversion of revolving financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-6A + Details
Name: | us-gaap_FinancingReceivableRevolvingConvertedToTermLoanDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The increase (decrease) during the reporting period in outstanding loans including accrued interest. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (a) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 + Details
Name: | us-gaap_IncreaseDecreaseInFinanceReceivables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 948 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477011/948-310-45-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481990/310-10-45-13 Reference 5: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A Reference 6: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 29 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-29 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (1) -Publisher SEC Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (2) -Publisher SEC Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Name Regulation S-K (SK) -Number 229 -Section 1404 -Paragraph a -Publisher SEC Reference 10: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 80 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-80 Reference 11: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-79 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-14 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_NotesReceivableGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_RetailPortfolioSegmentMember
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_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mbwm_OtherConsumerLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |