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Summary of Other Information Related to Stock Options (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Net cash proceeds from the exercise of stock options $ 46,400 $ 10,693 $ 35,218
Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average grant date fair value-per share $ 7.46 $ 7.02 $ 9.67
Intrinsic value of awards exercised $ 14,193 $ 4,852 $ 30,450
Net cash proceeds from the exercise of stock options $ 46,400 $ 10,693 $ 35,218