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Reconciliation of Weighted Average Common Shares Outstanding Used for Computation of Basic and Diluted Net Income Per Common Share (Detail) - shares
12 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2016
Earnings Per Share [Abstract]      
Basic weighted-average common shares outstanding 111,887,308 116,873,023 125,232,499
Effect of dilutive options, stock appreciation rights, restricted stock units and performance stock units 480,616 418,094 780,915
Diluted weighted-average shares outstanding 112,367,924 117,291,117 126,013,414