Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (390)
Net other comprehensive income (loss)	14	$ (52)
Ending balance	(376)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(204)
Net other comprehensive income (loss)	34	(67)
Ending balance	(170)
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)	(23)	12
Ending balance	(12)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(197)
Net other comprehensive income (loss)	3	$ 3
Ending balance	$ (194)