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Net Income per Common Share - Additional Information (Detail) - $ / shares
12 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Anti-dilutive common shares 906,294 812,957 692,942
Anti-dilutive common shares exercise price, minimum $ 25.60 $ 28.10 $ 25.60
Anti-dilutive common shares exercise price, maximum $ 46.02 $ 46.02 $ 46.02
Performance Stock Units (PSUs)      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Anti-dilutive common shares 2,509,536 3,165,152