Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 190	$ 182	$ 607	$ 524
Other comprehensive income (loss), net of tax:
Currency translation adjustments	38	(25)	47	(110)
Cash flow hedge adjustments	(32)	(7)	(48)	14
Postretirement benefits adjustments	3	6	9	13
Net other comprehensive income (loss)	9	(26)	8	(83)
Comprehensive income	$ 199	$ 156	$ 615	$ 441

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 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, attributable to parent entity.

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