Note 8 - Stock Compensation Plans (Details Textual) - USD ($) $ in Thousands		3 Months Ended
Jan. 05, 2019	Mar. 31, 2019	Mar. 31, 2018
Long-Term Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		1,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		57,684	57,829
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		865,004
Share-based Payment Arrangement, Expense		$ 67	$ 72
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total		$ 1,100	883
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		4 years 146 days
The 2000 Employee Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		0
Share-based Payment Arrangement, Expense		$ 0	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		180 days
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period		10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Total	19,200
The 2000 Employee Stock Incentive Plan [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		1,100,000

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

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

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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 number of grants made 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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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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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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