Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Weighted Average Number of Shares Outstanding Reconciliation
Weighted average number of common shares outstanding used to compute basic earnings per share	52,305	52,823	52,242	52,741
Dilutive effect of stock-based awards	705	650	678	634
Number of shares used to compute diluted earnings per share	53,010	53,473	52,920	53,375

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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-Publisher FASB
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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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