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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, 2016
Jan. 31, 2015
Jan. 31, 2014
Earnings Per Share [Line Items]      
Basic weighted-average common shares outstanding 125,232,499 136,651,899 147,014,869
Effect of dilutive options, stock appreciation rights, restricted stock units and performance stock units 780,915 1,540,835 2,211,037
Diluted weighted-average shares outstanding 126,013,414 138,192,734 149,225,906