Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (304)	$ (195)	$ (300)	$ (188)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(4)	(30)	(28)	(46)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	(4)	22	12	27
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	6	12	10	16
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(2)	4	(6)	(3)
Ending balance	(306)	(191)	(306)	(191)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	44	1	28	(4)
Ending balance	40	23	40	23
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(132)	(10)	(108)	6
Ending balance	(136)	(40)	(136)	(40)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(216)	(186)	(220)	(190)
Ending balance	$ (210)	$ (174)	$ (210)	$ (174)