Weighted-Average Fair Value of Stock Options and Employee Stock Purchase Rights using Weighted-Average Assumptions (Detail) - $ / shares	3 Months Ended	6 Months Ended
Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Stock Options
Weighted-average assumptions
Weighted-average fair value of grants per share	$ 4.64	$ 1.75	$ 4.63	$ 1.74
Expected volatility	41.79%	44.14%	40.43%	44.11%
Risk free interest rate	1.87%	0.94%	1.77%	0.94%
Expected term of options (in years)	4 years 4 months 24 days	4 years 3 months 19 days	4 years 1 month 6 days	4 years 3 months 19 days
Dividend yield	0.00%	0.00%	0.00%	0.00%
Stock Purchase Rights
Weighted-average assumptions
Weighted-average fair value of grants per share			$ 2.74	$ 1.54
Expected volatility			40.66%	39.33%
Risk free interest rate			1.14%	0.76%
Expected term of options (in years)			8 months 27 days	1 year 11 months 5 days
Dividend yield			0.00%	0.00%

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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