Net Income per Share - Schedule of Weighted Average Number of Shares (Details) - shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Basic weighted-average ordinary shares outstanding (in shares)	161,618	171,439	162,433	171,422
Dilutive effect of stock options (in shares)	568	883	601	905
Dilutive effect of unvested restricted securities (in shares)	292	371	466	448
Diluted weighted-average ordinary shares outstanding (in shares)	162,478	172,693	163,500	172,775

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

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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.

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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.

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