Reconciles the Denominators of the Company's Calculation for Basic and Diluted Net Income per Share (Detail) - shares shares in Thousands	3 Months Ended	9 Months Ended
Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Schedule Of Earnings Per Share Basic and Diluted [Line Items]
Shares used in basic per share computation	53,032	52,740	52,928	52,724
Shares used in diluted per share computation	54,302	53,926	54,181	53,952
Employee Stock Option
Schedule Of Earnings Per Share Basic and Diluted [Line Items]
Effect of dilutive stock outstanding	441	294	391	278
Restricted Stock Units (RSUs)
Schedule Of Earnings Per Share Basic and Diluted [Line Items]
Effect of dilutive stock outstanding	829	892	862	950

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
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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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