Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Before Tax:
Net other comprehensive income (loss)		$ (8)	$ 17	$ (13)	$ (27)
Tax Effect:
Net other comprehensive income (loss)		(7)	(22)	12	(30)
Net of Tax:
Net other comprehensive income (loss)		(15)	(5)	(1)	(57)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(25)	(4)	3	(72)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		(25)	(4)	3	(72)
Tax Effect:
Net gain (loss)		0	(14)	6	(13)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		0	(14)	6	(13)
Net of Tax:
Net gain (loss)		(25)	(18)	9	(85)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		(25)	(18)	9	(85)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		7	23	(29)	52
Reclassification to earnings	[1]	5	(9)	3	(19)
Net other comprehensive income (loss)		12	14	(26)	33
Tax Effect:
Net gain (loss)		(3)	(9)	11	(20)
Reclassification to earnings	[1]	(2)	4	(1)	8
Net other comprehensive income (loss)		(5)	(5)	10	(12)
Net of Tax:
Net gain (loss)		4	14	(18)	32
Reclassification to earnings	[1]	3	(5)	2	(11)
Net other comprehensive income (loss)		7	9	(16)	21
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(1)	0	0	0
Reclassification to earnings	[2]	6	7	10	12
Net other comprehensive income (loss)		5	7	10	12
Tax Effect:
Net gain (loss)		0	0	0	0
Reclassification to earnings	[2]	(2)	(3)	(4)	(5)
Net other comprehensive income (loss)		(2)	(3)	(4)	(5)
Net of Tax:
Net gain (loss)		(1)	0	0	0
Reclassification to earnings	[2]	4	4	6	7
Net other comprehensive income (loss)		$ 3	$ 4	$ 6	$ 7

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

[2] Pre-tax amount is a component of pension and other postretirement benefit expense (as shown in Note 7, except for amounts related to non-U.S. benefit plans, about which no information is presented in Note 7 due to immateriality).