Derivative Financial Instruments and Hedging Activities (Fair Value of Derivatives in a Gain (Loss) Position) (Details) - Currency derivatives [Member] - USD ($) $ in Millions	Apr. 30, 2019	Apr. 30, 2018
Fair value of derivatives in a gain position [Member] | Not designated as hedges [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	$ 0	$ 1
Fair value of derivatives in a loss position [Member] | Not designated as hedges [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	(5)
Cash Flow Hedging [Member] | Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	22	1
Cash Flow Hedging [Member] | Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	21	2
Cash Flow Hedging [Member] | Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	4
Cash Flow Hedging [Member] | Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	2
Cash Flow Hedging [Member] | Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	(1)	0
Cash Flow Hedging [Member] | Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	(2)	(2)
Cash Flow Hedging [Member] | Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Accrued expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	(5)	(23)
Cash Flow Hedging [Member] | Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	$ (1)	$ (18)