Note 11 - Federal Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 0	$ 0	$ 1,336,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(100,000)	(100,000)
Deferred Tax Assets, Capital Loss Carryforwards	94,000	94,000
Unrecognized Tax Benefits, Ending Balance	0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	0	0
Firstbank Corporation [Member]
Deferred Tax Assets, Capital Loss Carryforwards	$ 100,000	$ 100,000