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Percentage of Total Accounts Receivable (Detail)
Jan. 31, 2013
Jan. 31, 2012
Customer A
   
Accounts Receivable [Line Items]    
Receivables from customers as percentage of total accounts receivable 7.00% 4.00%
Customer B
   
Accounts Receivable [Line Items]    
Receivables from customers as percentage of total accounts receivable 5.00% 9.00%
Customer C
   
Accounts Receivable [Line Items]    
Receivables from customers as percentage of total accounts receivable 11.00% 14.00%