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Weighted Average Assumptions Relating to Valuation of Stock Options (Detail) (USD $)	12 Months Ended
	Apr. 27, 2013	Apr. 28, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of grants	$ 7.80	$ 9.85
Volatility	86.13%	78.52%
Risk-free interest rate	0.67%	0.92%
Expected life	5 years	5 years
Expected 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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