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Deferred Costs (Detail) - USD ($)
$ in Millions
3 Months Ended
Apr. 30, 2019
Apr. 30, 2018
Jan. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]      
Deferred sales commission $ 262   $ 264
Amortization of deferred costs $ 21 $ 16