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
Before Tax:
Net other comprehensive income (loss)		$ 21		$ 2		$ 24	$ 10
Tax Effect:
Net other comprehensive income (loss)		(6)		5		15	(4)
Net of Tax:
Net other comprehensive income (loss)		15	$ 24	7	$ (1)	39	6
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		5		6		58	(2)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		5		6		58	(2)
Tax Effect:
Net gain (loss)		(1)		5		8	(1)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		(1)		5		8	(1)
Net of Tax:
Net gain (loss)		4		11		66	(3)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		4		11		66	(3)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		14		(2)		(35)	13
Reclassification to earnings	[1]	(5)		(6)		(16)	(10)
Net other comprehensive income (loss)		9		(8)		(51)	3
Tax Effect:
Net gain (loss)		(4)		0		8	(3)
Reclassification to earnings	[1]	1		1		4	2
Net other comprehensive income (loss)		(3)		1		12	(1)
Net of Tax:
Net gain (loss)		10		(2)		(27)	10
Reclassification to earnings	[1]	(4)		(5)		(12)	(8)
Net other comprehensive income (loss)		6		(7)		(39)	2
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	7		4		17	9
Net other comprehensive income (loss)		7		4		17	9
Tax Effect:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	(2)		(1)		(5)	(2)
Net other comprehensive income (loss)		(2)		(1)		(5)	(2)
Net of Tax:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	5		3		12	7
Net other comprehensive income (loss)		$ 5		$ 3		12	$ 7
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 six months ended October 31, 2020, $4 of the pre-tax amount of $17 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.