Goodwill and Other Intangible Assets (Details) $ in Millions	3 Months Ended
Jul. 31, 2019 USD ($)
Goodwill [Roll Forward]
Balance at April 30, 2019	$ 753
Acquisition (Note 15)	11
Foreign currency translation adjustment	(10)
Balance at July 31, 2019	754
Indefinite-lived Intangible Assets [Roll Forward]
Balance at April 30, 2019	645
Acquisition (Note 15)	12
Foreign currency translation adjustment	(3)
Balance at July 31, 2019	$ 654

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an acquisition.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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