Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Apr. 30, 2015	Apr. 30, 2014
Deferred tax assets:
Postretirement and other benefits	$ 164	$ 139
Accrued liabilities and other	22	30
Inventories	12us-gaap_DeferredTaxAssetsInventory	8us-gaap_DeferredTaxAssetsInventory
Loss and credit carryforwards	46	52
Valuation allowance	(27)	(34)
Total deferred tax assets, net	217us-gaap_DeferredTaxAssetsNet	195us-gaap_DeferredTaxAssetsNet
Deferred tax liabilities:
Intangible assets	(207)	(184)
Property, plant, and equipment	(61)	(49)
Other	(31)us-gaap_DeferredTaxLiabilitiesOther	(21)us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax liabilities	(299)us-gaap_DeferredIncomeTaxLiabilities	(254)us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax liability	$ (82)us-gaap_DeferredTaxLiabilities	$ (59)us-gaap_DeferredTaxLiabilities

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory.

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Amount before allocation of valuation allowances of deferred tax asset attributable to other deductible tax carryforwards not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from postretirement benefits.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets including goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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