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Schedule of Assumptions Used to Calculate Weighted Average Fair Value of Stock Option Grants (Detail)	9 Months Ended
	Sep. 28, 2012	Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	43.30%	46.50%
Risk-free interest rate	0.90%	2.10%
Expected term (in years)	5 years 3 months 18 days	5 years 3 months 18 days
Expected dividend yield	2.00%	1.50%

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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