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
Before Tax:
Net other comprehensive income (loss)		$ 2			$ 8			$ 26	$ 17
Tax Effect:
Net other comprehensive income (loss)		17			0			32	(3)
Net of Tax:
Net other comprehensive income (loss)		19	$ 15	$ 24	8	$ 7	$ (1)	58	14
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		39			5			97	3
Reclassification to earnings		0			0			0	0
Net other comprehensive income (loss)		39			5			97	3
Tax Effect:
Net gain (loss)		8			1			16	0
Reclassification to earnings		0			0			0	0
Net other comprehensive income (loss)		8			1			16	0
Net of Tax:
Net gain (loss)		47			6			113	3
Reclassification to earnings		0			0			0	0
Net other comprehensive income (loss)		47			6			113	3
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(39)			4			(73)	17
Reclassification to earnings	[1]	(4)			(5)			(21)	(16)
Net other comprehensive income (loss)		(43)			(1)			(94)	1
Tax Effect:
Net gain (loss)		9			(1)			17	(4)
Reclassification to earnings	[1]	1			1			5	4
Net other comprehensive income (loss)		10			0			22	0
Net of Tax:
Net gain (loss)		(30)			3			(56)	13
Reclassification to earnings	[1]	(3)			(4)			(16)	(12)
Net other comprehensive income (loss)		(33)			(1)			(72)	1
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		0			0			0	0
Reclassification to earnings	[2]	6			4			23	13
Net other comprehensive income (loss)		6			4			23	13
Tax Effect:
Net gain (loss)		0			0			0	0
Reclassification to earnings	[2]	(1)			(1)			(6)	(3)
Net other comprehensive income (loss)		(1)			(1)			(6)	(3)
Net of Tax:
Net gain (loss)		0			0			0	0
Reclassification to earnings	[2]	5			3			17	10
Net other comprehensive income (loss)		$ 5			$ 3			17	$ 10
Gain on sale of business [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Reclassification to earnings								$ 4

[1] Pre-tax amount for each period is classified as sales in the accompanying condensed consolidated statements of operations.

[2] For the nine months ended January 31, 2021, $4 of the pre-tax amount of $23 is classified in gain on sale of business in the accompanying condensed consolidated statements of operations. Otherwise, the pre-tax amount for each period is classified as non-operating postretirement expense.