Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Jul. 31, 2018	Jul. 31, 2017
Before Tax:
Net other comprehensive income (loss)		$ 28	$ (5)
Tax Effect:
Net other comprehensive income (loss)		(14)	19
Net of Tax:
Net other comprehensive income (loss)		14	14
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(5)	28
Reclassification to earnings		0	0
Net other comprehensive income (loss)		(5)	28
Tax Effect:
Net gain (loss)		(7)	6
Reclassification to earnings		0	0
Net other comprehensive income (loss)		(7)	6
Net of Tax:
Net gain (loss)		(12)	34
Reclassification to earnings		0	0
Net other comprehensive income (loss)		(12)	34
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		27	(36)
Reclassification to earnings	[1]	2	(2)
Net other comprehensive income (loss)		29	(38)
Tax Effect:
Net gain (loss)		(6)	14
Reclassification to earnings	[1]	0	1
Net other comprehensive income (loss)		(6)	15
Net of Tax:
Net gain (loss)		21	(22)
Reclassification to earnings	[1]	2	(1)
Net other comprehensive income (loss)		23	(23)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		0	1
Reclassification to earnings	[2]	4	4
Net other comprehensive income (loss)		4	5
Tax Effect:
Net gain (loss)		0	0
Reclassification to earnings	[2]	(1)	(2)
Net other comprehensive income (loss)		(1)	(2)
Net of Tax:
Net gain (loss)		0	1
Reclassification to earnings	[2]	3	2
Net other comprehensive income (loss)		$ 3	$ 3

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

[2] Pre-tax amount is classified as non-operating postretirement expense in the accompanying condensed consolidated statements of operations.