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Note 12 - Stock-based Compensation (Details) - USD ($) |  |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
May. 28, 2015 | Jan. 02, 2015 | Jun. 01, 2014 | Jun. 30, 2014 | Dec. 31, 2015 | Dec. 31, 2014
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares) |  |  |  |  | 215,000 |
Stock Issued During Period, Shares, Issued for Services (in Shares) | 14,100 |  |  |  |  |
Allocated Share-based Compensation Expense (in Dollars) | $ 300,000 |  |  |  |  |
Stock Issued For Services Share-based Compensation Expense Period | 12 months |  |  |  |  |
Director [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Stock Issued During Period, Shares, Issued for Services (in Shares) |  | 5,994 |  |  |  |
Allocated Share-based Compensation Expense (in Dollars) |  | $ 100,000 |  |  |  |
Stock Issued For Services Share-based Compensation Expense Period |  | 5 months |  |  |  |
Firstbank Plans [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in Shares) |  |  |  |  | 0 | 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value (in Dollars) |  |  |  |  | $ 1,500,000 |
Firstbank Corporation [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in Shares) |  |  | 282,200 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number (in Shares) |  |  | 258,400 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares (in Shares) |  |  |  |  | 23,800 |
Options Granted During 2006, 2007 And 2008 [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  | 2 years |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period |  |  |  |  | 7 years |
Restricted Stock Granted In 2012 [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  | 2 years |
Restricted Stock Granted In 2014 And 2015 [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  | 3 years |
Stock Options Granted During 2014 And 2015 [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  | 2 years |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period |  |  |  |  | 7 years |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent |  |  |  |  | 110.00% |
Restricted Stock [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost (in Dollars) |  |  |  | $ 200,000 |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  |  |  |  | 3 years |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options (in Dollars) |  |  |  |  | $ 3,000,000 |
Employee Stock Option [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  |  |  |  | 2 years |
Employee Stock Option [Member] | Firstbank Corporation [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period |  |  |  |  | 10 years |
Stock Option Grants For 50 Shares Or Less [Member] | Firstbank Corporation [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  | 1 year |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  |  |  |  | 20.00% |
Maximum [Member] |  |  |  |  |  |
Note 12 - Stock-based Compensation (Details) [Line Items] |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options (in Dollars) |  |  |  |  | $ 100,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value (in Dollars) |  |  |  |  | $ 0 |

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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