Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2021	Jan. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (547)				$ (547)
Net other comprehensive income (loss)	$ 19	$ 15	24	$ 8	$ 7	$ (1)	58	$ 14
Ending balance	(489)						(489)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(302)				(302)
Net other comprehensive income (loss)	47			6			113	3
Ending balance	(189)						(189)
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)	(33)			(1)			(72)	1
Ending balance	(12)						(12)
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			17	$ 10
Ending balance	(288)						$ (288)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net other comprehensive income (loss)	$ 19	$ 15	$ 24	$ 8	$ 7	$ (1)