Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Cash Flow Hedging [Member] | Currency derivatives [Member]
Derivative instrument gains and losses affecting statements of operations
Net gain (loss) recognized in AOCI	$ 29	$ 71	$ 66	$ 118
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	16	46	20
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	5	19	9	31
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	$ (2)	$ 11	$ 2	$ 5