Note 3 - Loans and Allowance for Loan Losses - Nonaccrual Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
With no related allowance recorded, principal balance	$ 1,326	$ 1,824
With related allowance recorded, principal balance	8,417	3,918
Related allowance	3,894	2,134
Total principal balance	9,743	5,742
Commercial Portfolio Segment [Member]
With no related allowance recorded, principal balance	25	657
With related allowance recorded, principal balance	7,234	2,110
Related allowance	3,675	1,732
Total principal balance	7,259	2,767
Commercial Portfolio Segment [Member] \| Commercial and Industrial [Member]
With no related allowance recorded, principal balance	25	615
With related allowance recorded, principal balance	1,702	2,110
Related allowance	1,204	1,732
Commercial Portfolio Segment [Member] \| Vacant Land and Land Development and Residential Construction Loan [Member]
With no related allowance recorded, principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
Commercial Portfolio Segment [Member] \| Real Estate Owner Occupied Loan [Member]
With no related allowance recorded, principal balance	0	42
With related allowance recorded, principal balance	0	0
Related allowance	0	0
Commercial Portfolio Segment [Member] \| Real Estate Non Owner Occupied Loan [Member]
With no related allowance recorded, principal balance	0	0
With related allowance recorded, principal balance	5,532	0
Related allowance	2,471	0
Commercial Portfolio Segment [Member] \| Real Estate Multi Family and Residential Rental Loan [Member]
With no related allowance recorded, principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
Retail Portfolio Segment [Member]
With no related allowance recorded, principal balance	1,301	1,167
With related allowance recorded, principal balance	1,183	1,808
Related allowance	219	402
Total principal balance	2,484	2,975
Retail Portfolio Segment [Member] \| One to Four Family Mortgages [Member]
With no related allowance recorded, principal balance	1,301	1,167
With related allowance recorded, principal balance	1,183	1,808
Related allowance	219	402
Retail Portfolio Segment [Member] \| Other Consumer Loans [Member]
With no related allowance recorded, principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	$ 0	$ 0

MERCANTILE BANK CORP 10-Q