Derivative Financial Instruments and Hedging Activities (Fair Value of Derivatives in a Gain (Loss) Position) (Details) - Currency derivatives [Member] - USD ($) $ in Millions	Apr. 30, 2018	Apr. 30, 2017
Fair value of derivatives in a gain position [Member] | Not designated as hedges [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	$ 0	$ 2
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	1	0
Fair value of derivatives in a loss position [Member] | Not designated as hedges [Member] | Other Current Assets [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	(5)	(1)
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	1	9
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	2	21
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	4	2
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	2	1
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	0	(4)
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	(23)	(8)
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	$ (18)	$ (4)