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Note 1 - Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 01, 2014 USD ($)
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Number of Unconsolidated Business Trusts Formed to Issue Trust Preferred Securities	5
Number of Operating Segments	1
Loans and Leases Receivable, Deferred Income	$ 1,400,000	$ 1,100,000
Interest Income on Commercial and Mortgage Loans, Discontinued Period	90 days
Maximum Delinquency Period for Consumer and Credit Card Loans to be Charged-off	120 days
Repossessed Assets	$ 1,300,000	$ 2,000,000
Firstbank Corporation [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 1,500,000,000		$ 1,452,880,000
Business Combination, Branches Acquired	46		46
Core Deposits [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
Minimum [Member] | Building Improvements [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Minimum [Member] | Furniture and Fixtures [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member] | Building Improvements [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life	33 years
Maximum [Member] | Furniture and Fixtures [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life	7 years

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The number of unconsolidated business trusts formed to issue trust preferred securities.

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Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of assets acquired at the acquisition date.

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Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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