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Stock-Based Compensation - Weighted-Average Assumptions Used in Estimating Fair Values of Stock Options Granted (Detail)	3 Months Ended
	Mar. 31, 2013	Apr. 01, 2012
Schedule Of Stock Options [Line Items]
Risk-free rate	2.10%	2.00%
Expected dividend yield	0.00%	1.20%
Expected volatility	42.00%	44.00%
Expected term (in years)	5 years 10 months 24 days	5 years 8 months 12 days

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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