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Note 2 - Business Combination (Details Textual) | Jun. 01, 2014 USD ($) shares | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
--- | --- | --- | ---
Goodwill, Ending Balance |  | $ 49,473,000 | $ 49,473,000
Firstbank Corporation [Member] |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total | $ 1,500,000,000 |  |
Business Combination Branches Acquired | 46 |  |
Business Acquisition Conversion of Stock Per Share | shares | 1 |  |
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares | 8,087,272 |  |
Goodwill, Ending Balance | $ 49,500,000 |  |
Business Acquisition, Goodwill, Expected Tax Deductible Amount | $ 0 |  |

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- Definition The number of banking branches acquired in a business combination. + References No definition available. + Details
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- Definition Number of shares of equity interests issued or issuable to acquire entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
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- Definition The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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