Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax	$ (350)	$ (300)
Currency translation adjustments	(23)	(114)	$ (4)
Cash flow hedge adjustments	(17)	32	(4)
Postretirement benefits adjustments	(10)	(30)	31
Net other comprehensive income (loss)	(50)	(112)	$ 23
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax	(131)	(108)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax	11	28
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax	$ (230)	$ (220)