Shareholders' Equity - Weighted- Average Assumptions for Determining Fair Value (Detail) (USD $)	12 Months Ended
	Feb. 02, 2013	Jan. 28, 2012	Jan. 29, 2011
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	4 years	4 years	4 years
Expected dividends
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 months	6 months	6 months
Expected dividends
Minimum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock volatility	87.00%	83.00%	79.00%
Risk-free interest rates	0.50%	0.60%	1.00%
Minimum [Member] | ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock volatility		54.00%	60.00%
Risk-free interest rates	0.10%	0.20%	0.30%
Maximum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock volatility	88.00%	87.00%	82.00%
Risk-free interest rates	0.90%	1.60%	2.00%
Maximum [Member] | ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock volatility	71.00%	87.00%	97.00%
Risk-free interest rates	0.20%	0.60%	0.40%