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Related-Party Transactions (Detail) - USD ($)
$ in Millions
12 Months Ended
Jan. 31, 2019
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2014
Related Party Transaction [Line Items]        
Lease term period, in years       95 years
Chairman, Mr. Duffield        
Related Party Transaction [Line Items]        
Lease term period, in years 8 years      
Rent expense $ 11 $ 8 $ 8