Derivative Financial Instruments (Details) (Currency derivatives [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Cash Flow Hedging [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) recognized in AOCI	$ 71	$ 10	$ 118	$ 5
Net Sales [Member] | Cash Flow Hedging [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) reclassified from AOCI into income	16	(1)	20	0
Net Sales [Member] | Not designated as hedges [Member]
Derivative instrument gains and losses affecting statements of operations
Gain (loss) on derivative instruments recognized in income	19	5	31	4
Other Income [Member] | Not designated as hedges [Member]
Derivative instrument gains and losses affecting statements of operations
Gain (loss) on derivative instruments recognized in income	$ 11	$ 2	$ 5	$ 4