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Assumptions Used to Value Option Grants (Detail) (Stock Options)	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years 4 months 24 days	6 years 6 months	6 years 7 months 6 days
Risk-free interest rate	1.40%	3.10%	3.20%
Volatility	39.00%	39.00%	40.00%
Dividend yield	0.00%	0.00%	0.00%

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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