Derivative Financial Instruments (Gain (Loss) on Derivatives Recognized in Consolidated Statement of Operations) (Details) (Currency derivatives [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014
Cash Flow Hedging [Member]
Fair values of derivative instruments affecting statements of operations
Net gain (loss) recognized in AOCI	$ 96	$ (7)
Net Sales [Member] | Cash Flow Hedging [Member]
Fair values of derivative instruments affecting statements of operations
Net gain (loss) reclassified from AOCI into earnings	41	0
Net Sales [Member] | Not designated as hedges [Member]
Fair values of derivative instruments affecting statements of operations
Net gain (loss) recognized in earnings	26	1
Other Income [Member] | Not designated as hedges [Member]
Fair values of derivative instruments affecting statements of operations
Net gain (loss) recognized in earnings	$ 4	$ 10