Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (547)			$ (547)
Net other comprehensive income (loss)	$ 15	24	$ 7	$ (1)	39	$ 6
Ending balance	(508)				(508)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(302)			(302)
Net other comprehensive income (loss)	4		11		66	(3)
Ending balance	(236)				(236)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		60			60
Net other comprehensive income (loss)	6		(7)		(39)	2
Ending balance	21				21
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(305)			(305)
Net other comprehensive income (loss)	5		3		12	$ 7
Ending balance	(293)				$ (293)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net other comprehensive income (loss)	$ 15	$ 24	$ 7	$ (1)