Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Cash Flow Hedging [Member] | Currency derivatives [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) recognized in AOCI	$ 9	$ 42	$ 38	$ 47
Cash Flow Hedging [Member] | Treasury Lock [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) recognized in AOCI			8	0
Net Sales [Member] | Cash Flow Hedging [Member] | Currency derivatives [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) reclassified from AOCI into income	17	6	30	4
Net Sales [Member] | Not Designated as Hedging Instrument [Member] | Currency derivatives [Member]
Derivative instrument gains and losses affecting statements of operations
Gain (loss) on derivative instruments recognized in income	0	11	3	8
Other Income [Member] | Not Designated as Hedging Instrument [Member] | Currency derivatives [Member]
Derivative instrument gains and losses affecting statements of operations
Gain (loss) on derivative instruments recognized in income	$ 0	$ 3	$ 4	$ (6)