Derivative Financial Instruments and Hedging Activities (Details 1) - Currency derivatives [Member] - USD ($) $ in Millions	Jan. 31, 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	$ 3	$ 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	0	0
Fair value of derivatives in a gain position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	21
Fair value of derivatives in a gain position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	9
Fair value of derivatives in a gain position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Accrued Expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	4	2
Fair value of derivatives in a gain position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	1	1
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	(1)	(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	(1)
Fair value of derivatives in a loss position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [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 loss position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	(4)
Fair value of derivatives in a loss position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Accrued Expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	(40)	(8)
Fair value of derivatives in a loss position [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	$ (34)	$ (4)

Fair value of derivatives in a gain position [Member] | Not designated as hedges [Member] | Other Current Assets [Member]

Fair value of derivatives in a gain position [Member] | Not designated as hedges [Member] | Accrued Expenses [Member]

Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Current Assets [Member]

Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Assets [Member]

Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Accrued Expenses [Member]

Fair value of derivatives in a gain position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]

Fair value of derivatives in a loss position [Member] | Not designated as hedges [Member] | Other Current Assets [Member]

Fair value of derivatives in a loss position [Member] | Not designated as hedges [Member] | Accrued Expenses [Member]

Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Current Assets [Member]

Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Assets [Member]

Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Accrued Expenses [Member]

Fair value of derivatives in a loss position [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]