Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Jul. 31, 2020	Jul. 31, 2019
Before Tax:
Net other comprehensive income (loss)		$ 3	$ 7
Tax Effect:
Net other comprehensive income (loss)		21	(8)
Net of Tax:
Net other comprehensive income (loss)		24	(1)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		53	(8)
Reclassification to earnings		0	0
Net other comprehensive income (loss)		53	(8)
Tax Effect:
Net gain (loss)		9	(5)
Reclassification to earnings		0	0
Net other comprehensive income (loss)		9	(5)
Net of Tax:
Net gain (loss)		62	(13)
Reclassification to earnings		0	0
Net other comprehensive income (loss)		62	(13)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(49)	15
Reclassification to earnings	[1]	(11)	(4)
Net other comprehensive income (loss)		(60)	11
Tax Effect:
Net gain (loss)		12	(3)
Reclassification to earnings	[1]	3	1
Net other comprehensive income (loss)		15	(2)
Net of Tax:
Net gain (loss)		(37)	12
Reclassification to earnings	[1]	(8)	(3)
Net other comprehensive income (loss)		(45)	9
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		0	0
Reclassification to earnings	[2]	10	4
Net other comprehensive income (loss)		10	4
Tax Effect:
Net gain (loss)		0	0
Reclassification to earnings	[2]	(3)	(1)
Net other comprehensive income (loss)		(3)	(1)
Net of Tax:
Net gain (loss)		0	0
Reclassification to earnings	[2]	7	3
Net other comprehensive income (loss)		7	3
Non-operating postretirement expense [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Reclassification to earnings	[2]	6	$ 4
Gain on sale of business [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Reclassification to earnings	[2]	$ 4

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

[2] For three months ended July 31, 2019, the pre-tax amount of $4 is classified as non-operating postretirement expense in the accompanying condensed consolidated statements of operations. For three months ended July 31, 2020, $6 of the pre-tax amount is classified as non-operating postretirement expense; $4 of the pretax amount is classified in gain on sale of business.