Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Grants and Exercises (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Grants and Exercises [Line Items]
Cash received from stock option exercises	$ 282,000	$ 289,000	$ 227,000
Mercantile Plans [Member]
Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Grants and Exercises [Line Items]
Aggregate intrinsic value of stock options exercised	11,000	408,000	307,000
Cash received from stock option exercises	50,000	289,000	227,000
Tax benefit realized from stock option exercises	0	0	0
Weighted average per share fair value of stock options granted (in Dollars per share)	$ 2.72
Firstbank Plans [Member]
Note 12 - Stock-based Compensation (Details) - Summary of Stock Option Grants and Exercises [Line Items]
Aggregate intrinsic value of stock options exercised	333,000
Cash received from stock option exercises	232,000
Tax benefit realized from stock option exercises	$ 116,000

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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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-Publisher FASB

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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