Derivative Financial Instruments and Hedging Activities (Details 1) - USD ($) $ in Millions	Jan. 31, 2020	Apr. 30, 2019
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	$ 54	$ 43
Derivative Liability, Fair Value, Gross Liability	13	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	32	21
Derivative Liability, Fair Value, Gross Liability	(2)	(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	18	22
Derivative Liability, Fair Value, Gross Liability	(2)	(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	(7)	(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	(2)	(1)
Currency derivatives [Member] | Not designated as hedges [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Derivative Asset, Fair Value, Gross Asset	4	0
Derivative Liability, Fair Value, Gross Liability	$ 0	$ 0