Shareholder's Equity - Weighted- Average Assumptions for Determining Fair Value (Detail) (USD $)	9 Months Ended
	Oct. 27, 2012	Oct. 29, 2011
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	4 years	4 years
Expected dividends
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	6 months	6 months
Expected volatility	71.00%	54.00%
Risk-free interest rate	0.15%	0.20%
Expected dividends
Minimum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	87.00%	83.00%
Risk-free interest rate	0.53%	0.67%
Maximum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	88.00%	84.00%
Risk-free interest rate	0.92%	1.61%