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Share Repurchase Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jan. 31, 2020
Jan. 31, 2019
Jan. 31, 2018
Equity, Class of Treasury Stock [Line Items]      
Total cost $ (223,021) $ (131,642) $ (159,226)
Share repurchase program      
Equity, Class of Treasury Stock [Line Items]      
Number of common shares repurchased and subsequently retired 8,068,196 3,500,000  
Total cost $ 217,421 $ 121,397  
Average cost per share, including commissions $ 26.95 $ 34.68