Other Comprehensive Income Schedule of Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Before Tax:
Net other comprehensive income (loss)		$ 39	$ (6)	$ (14)
Tax Effect:
Net other comprehensive income (loss)		(24)	18	(26)
Net of Tax:
Net other comprehensive income (loss)		15	12	(40)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(16)	12	(71)
Reclassification to earnings		0	0	3
Net other comprehensive income (loss)		(16)	12	(68)
Tax Effect:
Net gain (loss)		(11)	12	(4)
Reclassification to earnings		0	0	(1)
Net other comprehensive income (loss)		(11)	12	(5)
Net of Tax:
Net gain (loss)		(27)	24	(75)
Reclassification to earnings		0	0	2
Net other comprehensive income (loss)		(27)	24	(73)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		69	(54)	41
Reclassification to earnings	[1]	(6)	11	(40)
Net other comprehensive income (loss)		63	(43)	1
Tax Effect:
Net gain (loss)		(16)	18	(17)
Reclassification to earnings	[1]	1	(3)	16
Net other comprehensive income (loss)		(15)	15	(1)
Net of Tax:
Net gain (loss)		53	(36)	24
Reclassification to earnings	[1]	(5)	8	(24)
Net other comprehensive income (loss)		48	(28)	0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(41)	5	28
Reclassification to earnings	[2]	33	20	25
Net other comprehensive income (loss)		(8)	25	53
Tax Effect:
Net gain (loss)		10	(2)	(10)
Reclassification to earnings	[2]	(8)	(7)	(10)
Net other comprehensive income (loss)		2	(9)	(20)
Net of Tax:
Net gain (loss)		(31)	3	18
Reclassification to earnings	[2]	25	13	15
Net other comprehensive income (loss)		$ (6)	$ 16	$ 33

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

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