Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Receivables allowance for doubtful accounts	$ 24	$ 24
Preferred stock, par value (in dollars per share)	$ 10	$ 10
Preferred stock, shares authorized (shares)	1,000	1,000
Preferred stock, shares issued (shares)	437	437
Preferred stock, shares outstanding (shares)	437	437
Preferred stock, percentage non-cumulative	5.00%	5.00%
Common stock, shares authorized (shares)	40,000,000	40,000,000
Common stock, shares issued (shares)	18,115,965	18,115,965
Common stock, shares outstanding (shares)	17,014,882	16,856,414
Treasury stock (shares)	1,101,083	1,259,551

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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The percentage rate used to calculate dividend payments on preferred stock.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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