Note 8 - Earnings Per Share - Shares Used to Calculate Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Weighted average number of shares used in computation of basic earnings per share (in shares)	50,645	50,367	50,627	49,942
Additional shares from the assumed exercise of employee stock options (in shares)	318	500	358	727
Weighted average number of shares used in computation of diluted earnings per share (in shares)	50,963	50,867	50,985	50,669

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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