Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Activity from Grants Issued under Various Firstbank Plans (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Activity from Grants Issued under Various Firstbank Plans [Line Items]
Outstanding, shares	35,335	60,876	152,896	214,903
Outstanding, weighted average exercise price	$ 31.09	$ 33.11	$ 26.15	$ 22.40
Options exercisable at year-end	28,847	60,876	152,896
Options exercisable at year-end	$ 33.11	$ 33.11	$ 26.15
Granted	6,488	0	0
Granted	$ 22.15
Exercised	(2,845)	(51,055)	(50,930)
Exercised	$ 17.74	$ 13.72	$ 10.83
Forfeited or expired	(29,184)	(40,965)	(11,077)
Forfeited or expired	$ 34.60	$ 31.30	$ 23.77
Firstbank Plans [Member]
Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Activity from Grants Issued under Various Firstbank Plans [Line Items]
Outstanding, shares	217,982	0
Outstanding, weighted average exercise price	$ 14.89	$ 0
Options exercisable at year-end	210,777
Options exercisable at year-end	$ 15.22
Granted	0
Granted	$ 0
Replaced as part of merger	282,178
Replaced as part of merger	$ 15.48
Exercised	(27,740)
Exercised	$ 8.34
Forfeited or expired	(36,456)
Forfeited or expired	$ 24.46

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Gross number of share options (or share units) replaced as part of merger during the period

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Weighted average per share amount at which grantees can acquire shares of common stock with respect to stock options which were replaced as part of merger.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Publisher FASB

-Name Accounting Standards Codification

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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