Derivative Financial Instruments and Hedging Activities (Fair Value of Derivatives in a Gain (Loss) Position) (Details) - USD ($) $ in Millions	Apr. 30, 2020	Apr. 30, 2019
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	$ 79	$ 43
Derivative Liability, Fair Value, Gross Liability	(3)	(9)
Currency derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	49	21
Derivative Liability, Fair Value, Gross Liability	(1)	(2)
Currency derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Assets [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	30	22
Derivative Liability, Fair Value, Gross Liability	0	(1)
Currency derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	(5)
Currency derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	(1)
Currency derivatives [Member] | Not designated as hedges [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	$ (2)	$ 0