Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Before Tax:
Net other comprehensive income (loss)		$ (28)	$ (11)	$ (55)	$ (6)
Tax Effect:
Net other comprehensive income (loss)		2	(6)	(28)	(17)
Net of Tax:
Net other comprehensive income (loss)		(26)	(17)	(83)	(23)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(27)	(30)	(99)	(57)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		(27)	(30)	(99)	(57)
Tax Effect:
Net gain (loss)		2	0	(11)	(1)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		2	0	(11)	(1)
Net of Tax:
Net gain (loss)		(25)	(30)	(110)	(58)
Reclassification to earnings		0	0	0	0
Net other comprehensive income (loss)		(25)	(30)	(110)	(58)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		5	29	57	74
Reclassification to earnings	[1]	(15)	(17)	(34)	(46)
Net other comprehensive income (loss)		(10)	12	23	28
Tax Effect:
Net gain (loss)		(3)	(11)	(23)	(26)
Reclassification to earnings	[1]	6	7	14	18
Net other comprehensive income (loss)		3	(4)	(9)	(8)
Net of Tax:
Net gain (loss)		2	18	34	48
Reclassification to earnings	[1]	(9)	(10)	(20)	(28)
Net other comprehensive income (loss)		(7)	8	14	20
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		2	0	2	0
Reclassification to earnings	[2]	7	7	19	23
Net other comprehensive income (loss)		9	7	21	23
Tax Effect:
Net gain (loss)		(1)	0	(1)	0
Reclassification to earnings	[2]	(2)	(2)	(7)	(8)
Net other comprehensive income (loss)		(3)	(2)	(8)	(8)
Net of Tax:
Net gain (loss)		1	0	1	0
Reclassification to earnings	[2]	5	5	12	15
Net other comprehensive income (loss)		$ 6	$ 5	$ 13	$ 15

[1] Pre-tax amount is classified as net 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).