Summary of Significant Accounting Policies - Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Oct. 01, 2016	Sep. 26, 2015	Oct. 01, 2016	Sep. 26, 2015
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income	$ 19,512	$ 12,793	$ 28,258	$ 24,799
Weighted-average shares outstanding	27,237	29,654	27,878	29,697
Dilutive effect of employee stock options and restricted shares	541	463	545	556
Diluted weighted-average shares outstanding	27,778	30,117	28,423	30,253
Basic income per share	$ 0.72	$ 0.43	$ 1.01	$ 0.84
Diluted income per share	$ 0.70	$ 0.42	$ 0.99	$ 0.82
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	500	700	600	500

Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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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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