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Schedule of Estimated Fair Value of Stock Options Assumptions (Detail)	9 Months Ended
	Sep. 30, 2012	Oct. 02, 2011
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	3 years 6 months	4 years
Interest rate	0.40%	1.50%
Volatility-historical	56.00%	52.10%
Dividend yield	0.00%	0.00%
Stock Purchase Rights
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	6 months	6 months
Interest rate	0.11%	0.14%
Volatility-historical	42.70%	41.00%
Dividend yield	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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