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Concentration of Risk - Additional Information (Detail) - Vendor [Member]
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Purchases [Member]      
Concentration Risk [Line Items]      
Concentration Risk, Percentage 33.20% 23.70% 21.90%
Trade Accounts Payables [Member]      
Concentration Risk [Line Items]      
Concentration Risk, Percentage 42.70% 16.70% 55.10%