v3.25.3

Insider Trading Arrangements	3 Months Ended	9 Months Ended
Insider Trading Arrangements	Sep. 30, 2025	Sep. 30, 2025
Trading Arrangements, by Individual [Table]
Material Terms of Trading Arrangement [Text Block]		Item 5. Other Information. Not applicable.
Non-Rule 10b5-1 Arrangement Adopted [Flag]	false
Rule 10b5-1 Arrangement Adopted [Flag]	false
Rule 10b5-1 Arrangement Terminated [Flag]	false
Non-Rule 10b5-1 Arrangement Terminated [Flag]	false

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 1

+ Details

Name:	ecd_MtrlTermsOfTrdArrTextBlock
Namespace Prefix:	ecd_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 1

+ Details

Name:	ecd_NonRule10b51ArrAdoptedFlag
Namespace Prefix:	ecd_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 1

+ Details

Name:	ecd_NonRule10b51ArrTrmntdFlag
Namespace Prefix:	ecd_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 1

+ Details

Name:	ecd_Rule10b51ArrAdoptedFlag
Namespace Prefix:	ecd_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 1

+ Details

Name:	ecd_Rule10b51ArrTrmntdFlag
Namespace Prefix:	ecd_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 408
-Subsection a
-Paragraph 2
-Subparagraph A

+ Details

Name:	ecd_TradingArrByIndTable
Namespace Prefix:	ecd_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

MERCANTILE BANK CORP 10-Q