Derivatives - Schedule of Outstanding Foreign Currency Derivative Contracts Related Primarily to Intercompany Receivables and Payables (Detail) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	Apr. 30, 2019	Jan. 31, 2019
Derivative [Line Items]
Fair value of foreign currency derivative contracts	$ (14)	$ 25
Foreign currency derivative contracts
Derivative [Line Items]
Notional amount of foreign currency derivative contracts	$ 6,597	$ 4,496