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Note 2 - Securities (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2015 USD ($) | Dec. 31, 2014 USD ($)
Note 2 - Securities (Details) [Line Items] |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | $ 114,535,000 | $ 264,699,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  | 2,343,000 | 3,576,000
Available-for-sale Debt Securities, Amortized Cost Basis |  | 365,456,000 |
Available-for-sale Securities | [1] | $ 367,173,000 | 432,912,000
Debt Securities [Member] |  |  |
Note 2 - Securities (Details) [Line Items] |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions |  | 161 |
State of Michigan and all its Political Subdivisions [Member] |  |  |
Note 2 - Securities (Details) [Line Items] |  |  |
Available-for-sale Debt Securities, Amortized Cost Basis |  | $ 106,000,000 | 113,100,000
Available-for-sale Securities |  | 106,900,000 | 113,900,000
All Other States and Their Political Subdivisions [Member] |  |  |
Note 2 - Securities (Details) [Line Items] |  |  |
Available-for-sale Debt Securities, Amortized Cost Basis |  | 25,900,000 | 30,000,000
Available-for-sale Securities |  | $ 26,000,000 | 30,000,000
Securities Other Than U.S. Government Agencies and the State of Michigan and Political Subdivisions [Member] | Stockholders' Equity, Total [Member] | Securities Issued Concentration Risk [Member] |  |  |
Note 2 - Securities (Details) [Line Items] |  |  |
Concentration Risk, Percentage |  | 10.00% |
U.S. Government Agency Debt Obligations and Mortgage-Backed Securities [Member] |  |  |
Note 2 - Securities (Details) [Line Items] |  |  |
Available-for-sale Securities, Restricted |  | $ 158,100,000 | $ 167,600,000
[1] | See Note 11 for a description of the fair value hierarchy as well as a disclosure of levels for classes of financial assets and liabilities.

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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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