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Note 2 - Business Combination (Details) | Jun. 01, 2014 USD ($) shares | Jun. 30, 2015 USD ($) | Dec. 31, 2014 USD ($)
--- | --- | --- | ---
Note 2 - Business Combination (Details) [Line Items] |  |  |
Goodwill |  | $ 49,473,000 | $ 49,473,000
Firstbank Corporation [Member] |  |  |
Note 2 - Business Combination (Details) [Line Items] |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets | $ 1,500,000,000 |  |
Business Combination, Branches Acquired | 46 |  |
Business Acquisition, Conversion of Stock Per Share (in Shares) | shares | 1 |  |
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in Shares) | shares | 8,087,272 |  |
Goodwill | $ 49,500,000 |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt | $ 36,100,000 |  |
Business Combination, Debt Assumed, Number of Trusts | 4 |  |
Firstbank Corporation [Member] | Estimate of Fair Value Measurement [Member] |  |  |
Note 2 - Business Combination (Details) [Line Items] |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt | $ 21,100,000 |  |
Minimum [Member] | Firstbank Corporation [Member] | Acquired Trusts [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Note 2 - Business Combination (Details) [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 1.27% |  |
Maximum [Member] | Firstbank Corporation [Member] | Acquired Trusts [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Note 2 - Business Combination (Details) [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 1.99% |  |

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