XML 130 R112.htm IDEA: XBRL DOCUMENT v3.25.0.1

Note 19 - Subordinated Notes (Details Textual) - USD ($) $ in Millions			12 Months Ended
	Jan. 14, 2022	Dec. 15, 2021	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]		Secured Overnight Financing Rate (SOFR) [Member]	Secured Overnight Financing Rate (SOFR) [Member]
Subordinated Notes [Member]
Subordinated Debt, Principal Amount	$ 15.0	$ 75.0
Subordinated Borrowing, Interest Rate		3.25%
Subordinated Borrowing, Redemption Price, Percentage of Principal Amount		100.00%
Debt Instrument, Basis Spread on Variable Rate		2.12%
Increase to Equity Capital From Issuance of Subordinated Long-term Debt	$ 15.0	$ 70.0
Debt Issuance Costs, Gross			$ 0.7	$ 1.0

X

- Definition

The amount of proceeds that being injected and increase to equity capital from the issuance of subordinated long-term debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	mbwm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Redemption price as a percentage of principal amount.

+ References

No definition available.

+ Details

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Namespace Prefix:	mbwm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Principal amount of subordinated debt.

+ References

No definition available.

+ Details

Name:	mbwm_SubordinatedDebtPrincipalAmount
Namespace Prefix:	mbwm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Indicates type of variable interest rate on debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 470
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477734/942-470-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Stated interest rate of the subordinated debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: