Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (350)
Net other comprehensive income (loss)	(52)	$ (4)
Ending balance	(402)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(131)
Net other comprehensive income (loss)	(67)	(24)
Ending balance	(198)
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)	12	16
Ending balance	23
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(230)
Net other comprehensive income (loss)	3	$ 4
Ending balance	$ (227)