Note 6 - Share-based Compensation (Details Textual) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares	5,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares	3,307,485
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 3.97
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total \| $	$ 0.6
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 182 days
Stock Appreciation Rights (SARs) [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total \| $	$ 0.1
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 219 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 3.97
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total \| $	$ 1.5
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 292 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 17.41
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total \| $	$ 2.5
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years 109 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 17.77
Performance Shares [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Shares [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Outside Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&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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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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Number of shares authorized for issuance under share-based payment arrangement.

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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.

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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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