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Assumptions Used in Calculating Estimated Fair Value of Stock Option Award (Detail)	6 Months Ended
	Jun. 30, 2012	Jul. 02, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility	36.50%	35.50%
Expected life	5 years 8 months 12 days	5 years 6 months
Risk-free interest rate	0.90%	2.12%
Dividend yield	2.29%	2.16%

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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