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Note 14 - Employee Benefits - Stock Options Outstanding by Grant Date (Details) - $ / shares | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Outstanding, shares (in shares) | 19,750 | 29,324 | 31,949
Outstanding, weighted average exercise price (in dollars per share) | $ 20.94 | $ 23.67 |
Exercisable, December 31 (in shares) | 19,750 |  |
Exercisable, December 31 (in dollars per share) | $ 20.94 |  |
Exercise Price Range 1 [Member] |  |  |
Exercise price (in dollars per share) | $ 23 |  |
Outstanding, shares (in shares) | 12,300 |  |
Outstanding, contractual average life (Year) | 310 days |  |
Outstanding, weighted average exercise price (in dollars per share) | $ 23 |  |
Exercisable, December 31 (in shares) | 12,300 |  |
Exercisable, December 31 (in dollars per share) | $ 23 |  |
Exercise Price Range 2 [Member] |  |  |
Exercise price (in dollars per share) | $ 17.55 |  |
Outstanding, shares (in shares) | 7,450 |  |
Outstanding, contractual average life (Year) | 3 years 127 days |  |
Outstanding, weighted average exercise price (in dollars per share) | $ 17.55 |  |
Exercisable, December 31 (in shares) | 7,450 |  |
Exercisable, December 31 (in dollars per share) | $ 17.55 |  |
Exercise Price Range 3 [Member] |  |  |
Exercise price (in dollars per share) |  |  |
Outstanding, shares (in shares) | 19,750 |  |
Outstanding, contractual average life (Year) |  |  |
Outstanding, weighted average exercise price (in dollars per share) |  |  |
Exercisable, December 31 (in shares) | 19,750 |  |
Exercisable, December 31 (in dollars per share) |  |  |

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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. + References No definition available. + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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