Stock-Based Compensation - Changes in Stock Options (Detail) - $ / shares	12 Months Ended
Dec. 27, 2017	Dec. 28, 2016
Shares
Outstanding-beginning balance (shares)	2,191,728	2,151,214
Grants (shares)	135,036	347,053
Exercised (shares)	(17,661)	(147,726)
Forfeited, cancelled or expired (shares)	0	(158,813)
Outstanding-ending balance (shares)	2,309,103	2,191,728
Vested and expected to vest at December 27, 2017 (shares)	2,289,313
Exercisable at December 27, 2017 (shares)	1,909,440
Weighted-Average Exercise Price
Outstanding-beginning balance (usd per share)	$ 7.26	$ 6.25
Grants (usd per share)	13.73	12.14
Exercised (usd per share)	5.26	6.62
Forfeited, cancelled or expired (usd per share)	0.00	8.20
Outstanding-ending balance (usd per share)	7.65	$ 7.26
Vested and expected to vest at December 27, 2017 (usd per share)	7.60
Exercisable at December 27, 2017 (usd per share)	$ 6.59

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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