Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (350)
Net other comprehensive income (loss)	$ (5)	$ (2)	(57)	$ (6)
Ending balance	(407)		(407)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(131)
Net other comprehensive income (loss)	(18)	(4)	(85)	(28)
Ending balance	(216)		(216)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			11
Net other comprehensive income (loss)	9	(4)	21	12
Ending balance	32		32
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(230)
Net other comprehensive income (loss)	4	$ 6	7	$ 10
Ending balance	$ (223)		$ (223)