Earnings per Share (Details) - shares shares in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Number of Shares Outstanding Reconciliation
Weighted average number of common shares outstanding used to compute basic earnings per share	52,333	52,503	53,192
Dilutive effect of stock-based awards	728	702	555
Number of shares used to compute diluted earnings per share	53,061	53,205	53,747

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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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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