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Note 2 - Securities (Details Textual) | Mar. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
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Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | 267 |
Debt Securities, Available-for-sale, Unrealized Loss Position, Total | $ 224,586,000 | $ 278,331,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total | 7,863,000 | 11,357,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held, Ending Balance | 0 |
Debt Securities, Available-for-sale, Amortized Cost, Total | 343,856,000 | 347,795,000
Debt Securities, Available-for-sale, Total | 337,876,000 | 337,366,000
State of Michigan and All Its Political Subdivisions [Member] |  |
Debt Securities, Available-for-sale, Amortized Cost, Total | 100,000,000 | 98,200,000
Debt Securities, Available-for-sale, Total | 101,000,000 | 97,400,000
All Other States and Their Political Subdivisions [Member] |  |
Debt Securities, Available-for-sale, Amortized Cost, Total | 8,000,000 | 8,700,000
Debt Securities, Available-for-sale, Total | 8,000,000 | 8,700,000
US Government Agency Debt Obligations and Mortgage Backed Securities [Member] |  |
Debt Securities, Available-for-sale, Restricted | $ 111,000,000 | $ 104,000,000

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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
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