Derivative Financial Instruments (Details 1) (Currency derivatives [Member], USD $) In Millions, unless otherwise specified	Jan. 31, 2015	Apr. 30, 2014
Fair value of derivatives in a gain position [Member] | Cash Flow Hedging [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	$ 77	$ 6
Fair value of derivatives in a gain position [Member] | Cash Flow Hedging [Member] | Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	39	2
Fair value of derivatives in a gain position [Member] | Cash Flow Hedging [Member] | Accrued Expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position		2
Fair value of derivatives in a gain position [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position		0
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	21	5
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] | Cash Flow Hedging [Member] | Other Current Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	(6)
Fair value of derivatives in a loss position [Member] | Cash Flow Hedging [Member] | Other Assets [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position	0	0
Fair value of derivatives in a loss position [Member] | Cash Flow Hedging [Member] | Accrued Expenses [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position		(6)
Fair value of derivatives in a loss position [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]
Fair values of derivative instruments
Fair value of derivatives in a gain (loss) position		(4)
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	0
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	$ (4)	$ 0