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Note 13 - Stock-based Compensation (Details Textual) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value | $ 3.8 | $ 5.4 | $ 0.9
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year) | 6 years 8 months 12 days |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 0.1 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year) | 5 years |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value | $ 0.1 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value | $ 2.1 | $ 1.8 | $ 1.5
ESPP [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date | 15.00% |  |
Employee Stock Purchase Plan, Offering Period (Month) | 6 months |  |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | 85.00% |  |
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total (in shares) | 67,729 | 42,235 |
Employee Stock Purchase Plan, Weighted Average Purchase Price of Shares Purchased (in shares) | 61.96 | 85.85 |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares) | 1,058,866 |  |
Share-based Payment Arrangement, Option [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year) | 10 years |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $ 4.3 |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | 2 years 7 months 6 days |  |
Share-based Payment Arrangement, Option [Member] | Minimum [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | 4 years |  |
Share-based Payment Arrangement, Option [Member] | Maximum [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | 5 years |  |
Restricted Stock [Member] |  |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $ 26.0 |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | 2 years 4 months 24 days |  |
Restricted Stock [Member] | Minimum [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | 3 years |  |
Restricted Stock [Member] | Maximum [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | 5 years |  |
Performance Shares [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | 3 years |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $ 0.8 |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | 1 year 9 months 18 days |  |
Percentage of Target Number Capable of Being Earned and Vesting, Lower Limit | 0.00% |  |
Percentage of Target Number Capable of Being Earned and Vesting, Upper Limit | 150.00% |  |
Long-Term Incentive Plan 2012 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year) | 10 years |  |

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- Definition The lower limit percent of target number capable of being earned and vesting at the end of a three-year performance period depending on the company's performance in the final year of the performance period and the award recipient's continued employment. + References No definition available. + Details
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- Definition The upper limit percent of target number capable of being earned and vesting at the end of a three-year performance period depending on the company's performance in the final year of the performance period and the award recipient's continued employment. + References No definition available. + Details
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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Discount rate from fair value on offering date that participants pay for shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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