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Share Repurchase Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Equity, Class of Treasury Stock [Line Items]      
Total cost $ 47,839 $ 475,424 $ 615,421
Share repurchase program      
Equity, Class of Treasury Stock [Line Items]      
Number of common shares repurchased and subsequently retired 1,324,700 14,961,710  
Total cost $ 45,787 $ 465,304  
Average cost per share, including commissions $ 34.56 $ 31.10