Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ / shares in Thousands, $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance	$ 40	$ 40
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized (in shares)	43,000,000	43,000,000
Common stock, issued (in shares)	19,091,288	19,040,273
Common stock, outstanding (in shares)	19,091,288	19,040,273

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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Face amount per share of no-par value common stock.

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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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