Derivative Financial Instruments and Hedging Activities (Fair Value of Derivatives in a Gain (Loss) Position) (Details) - USD ($) $ in Millions	Apr. 30, 2021	Apr. 30, 2020
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	$ 10	$ 79
Derivative Liability, Fair Value, Gross Liability	(38)	(3)
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	4	49
Derivative Liability, Fair Value, Gross Liability	(2)	(1)
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	0	30
Derivative Liability, Fair Value, Gross Liability	0	0
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	4	0
Derivative Liability, Fair Value, Gross Liability	(18)	0
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	1	0
Derivative Liability, Fair Value, Gross Liability	(18)	0
Currency derivatives [Member] | Not designated as hedges [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	1
Derivative Liability, Fair Value, Gross Liability	$ 0
Currency derivatives [Member] | Not designated as hedges [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset		0
Derivative Liability, Fair Value, Gross Liability		$ (2)