Note 6 - Stock-based Compensation (Details Textual)	3 Months Ended
Mar. 31, 2019 USD ($) $ / shares	Mar. 31, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 3.77
Incentive Plan [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 1,130,000
Incentive Plan [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Expense	$ 448,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years 255 days
Incentive Plan [Member] \| Restricted Stock [Member]
Share-based Payment Arrangement, Expense	$ 682,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years 255 days
Stock-based Compensation Expense [Member]
Share-based Payment Arrangement, Expense	$ 75,000	$ 86,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Exercise Price	9.65
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Exercise Price	15.48

Price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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-Publisher FASB
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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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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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