Note 4 - Common Stock - Changes in Common Stock Issued and Outstanding (Details) - shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Balance, shares issued (in shares)	184,735	184,735
Balance, treasury stock (in shares)	27,502	27,070
Balance, shares outstanding (in shares)	157,233	157,665
Purchase of stock (in shares)	618	432
Purchase of stock (in shares)	(618)	(432)
Balance, shares issued (in shares)	184,735	184,735
Balance, treasury stock (in shares)	28,120	27,502
Balance, shares outstanding (in shares)	156,615	157,233

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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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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Number of shares that have been repurchased during the period and are being held in treasury.

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