Net Income (Loss) per Share - Reconciliation of Basic and Diluted Shares (Detail) - 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:
Basic	34,833	33,640	34,638	33,425
Dilutive effects of:
Employee stock options, RSU’s and share based payment awards issued to employees	0	0		559
Diluted	34,833	33,640	34,638	33,984

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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