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Shareholders' Equity - Weighted- Average Assumptions for Determining Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Aug. 03, 2013	Jul. 28, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life		4 years
Expected dividends		$ 0
Stock Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility		87.00%
Risk-free interest rate		0.53%
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility		88.00%
Risk-free interest rate		0.92%
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	1 year	6 months
Expected volatility	63.00%	71.00%
Risk-free interest rate	0.11%	0.15%
Expected dividends

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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