Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Apr. 30, 2021	Apr. 30, 2020
Deferred tax assets:
Postretirement and other benefits	$ 90	$ 110
Accrued liabilities and other	47	23
Inventories	30	26
Lease liabilities	17	14
Derivative instruments	5	0
Loss and credit carryforwards	63	57
Valuation allowance	(20)	(22)
Total deferred tax assets, net	232	208
Deferred tax liabilities:
Intangible assets	(214)	(233)
Property, plant, and equipment	(89)	(90)
Right-of-use assets	(17)	(13)
Derivative instruments	0	(18)
Other	(11)	(16)
Total deferred tax liabilities	(331)	(370)
Net deferred tax liability	$ (99)	$ (162)