Accumulated Other Comprehensive Income Schedule of Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Before Tax:
Net other comprehensive income (loss)		$ (6)	$ (14)	$ (69)
Tax Effect:
Net other comprehensive income (loss)		18	(26)	19
Net of Tax:
Net other comprehensive income (loss)		12	(40)	(50)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		12	(71)	(22)
Reclassification to earnings		0	3	0
Net other comprehensive income (loss)		12	(68)	(22)
Tax Effect:
Net gain (loss)		12	(4)	(1)
Reclassification to earnings		0	(1)	0
Net other comprehensive income (loss)		12	(5)	(1)
Net of Tax:
Net gain (loss)		24	(75)	(23)
Reclassification to earnings		0	2	0
Net other comprehensive income (loss)		24	(73)	(23)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(54)	41	30
Reclassification to earnings	[1]	11	(40)	(60)
Net other comprehensive income (loss)		(43)	1	(30)
Tax Effect:
Net gain (loss)		18	(17)	(10)
Reclassification to earnings	[1]	(3)	16	23
Net other comprehensive income (loss)		15	(1)	13
Net of Tax:
Net gain (loss)		(36)	24	20
Reclassification to earnings	[1]	8	(24)	(37)
Net other comprehensive income (loss)		(28)	0	(17)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		5	28	(47)
Reclassification to earnings	[2]	20	25	30
Net other comprehensive income (loss)		25	53	(17)
Tax Effect:
Net gain (loss)		(2)	(10)	19
Reclassification to earnings	[2]	(7)	(10)	(12)
Net other comprehensive income (loss)		(9)	(20)	7
Net of Tax:
Net gain (loss)		3	18	(28)
Reclassification to earnings	[2]	13	15	18
Net other comprehensive income (loss)		$ 16	$ 33	$ (10)

[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 8, except for amounts related to non-U.S. benefit plans, about which no information is presented in Note 8 due to immateriality).