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Share-Based Compensation Expense Included in Selling, General and Administrative Expenses in Consolidated Statements of Income (Parenthetical) (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended
Jan. 31, 2013
Jan. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Reversal of share-based compensation expense $ 3,418 $ 8,800
Performance Share Units
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares, granted 320,200  
Performance Share Units | Former Executive Officer
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares, granted   1,054,466