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Summary of Other Information Related to Stock Options (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jan. 31, 2019
Jan. 31, 2018
Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Net cash proceeds from the exercise of stock options $ 13,618   $ 4,096
Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average grant date fair value—per share $ 17.12 $ 5.37 $ 7.31
Intrinsic value of awards exercised $ 4,369   $ 1,566
Net cash proceeds from the exercise of stock options $ 13,618   $ 4,096