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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 |

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