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Note 15 - Benefit Plans (Details Textual) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2014
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 5.00% |  |  | 4.25%
Defined Contribution Plan, Cost | $ 1.7 | $ 1.6 | $ 1.3 |
Interest Expense, Deferred Compensation Plan | $ 0.1 | $ 0.1 |  |
Common Stock Including Additional Paid in Capital [Member] |  |  |  |
Stock Issued During Period, Shares, Employee Stock Purchase Plans | 1,507 | 1,579 | 1,351 |
Stock Purchase Plan [Member] |  |  |  |
Common Stock, Capital Shares Reserved for Future Issuance | 250,000 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | 241,000 |  |  |
Maximum [Member] |  |  |  |
Interest Expense, Deferred Compensation Plan |  |  | $ 0.1 |
Other Liabilities [Member] |  |  |  |
Deferred Compensation Liability, Current and Noncurrent, Total | $ 2.7 | $ 3.0 |  |

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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