Note 7 - Share-based Compensation (Details Textual) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 10.09
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 1.3
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 7 months 6 days
Outside Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
Stock Appreciation Rights (SARs) [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 0.4
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 10.09
Restricted Stock [Member]
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)	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) \| $ / shares	$ 23.19
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 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)	2 years 4 months 24 days
Performance Shares [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	3 years
Performance Shares [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	5 years
Share-based Payment Arrangement, Tranche One [Member] \| Stock Options and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	1 year
Share-based Payment Arrangement, Tranche Two [Member] \| Stock Options and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	2 years

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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

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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.

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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.

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-Publisher FASB
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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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