Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 186us-gaap_NetIncomeLoss	$ 177us-gaap_NetIncomeLoss	$ 543us-gaap_NetIncomeLoss	$ 526us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Currency translation adjustments	(62)	(14)	(108)	(19)
Cash flow hedge adjustments	34	7	61	3
Postretirement benefits adjustments	4	5	20	24
Net other comprehensive income (loss)	(24)	(2)	(27)	8
Comprehensive income	$ 162us-gaap_ComprehensiveIncomeNetOfTax	$ 175us-gaap_ComprehensiveIncomeNetOfTax	$ 516us-gaap_ComprehensiveIncomeNetOfTax	$ 534us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans, attributable to parent entity.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss), attributable to parent entity.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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