Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Apr. 30, 2016	Apr. 30, 2015
Deferred tax assets:
Postretirement and other benefits	$ 183	$ 164
Accrued liabilities and other	10	22
Inventories	26	12
Loss and credit carryforwards	39	46
Valuation allowance	(25)	(27)
Total deferred tax assets, net	233	217
Deferred tax liabilities:
Intangible assets	(225)	(207)
Property, plant, and equipment	(83)	(61)
Other	(9)	(31)
Total deferred tax liabilities	(317)	(299)
Net deferred tax liability	$ (84)	$ (82)