Derivative Financial Instruments and Hedging Activities (Gain (Loss) on Derivatives Recognized in Consolidated Statement of Operations) (Details) - USD ($) $ in Millions	12 Months Ended
Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Currency derivatives [Member]
Derivative Instruments [Abstract]
Net gain (loss) recognized in AOCI	$ 69	$ (54)	$ 41
Designated as Hedging Instrument [Member] \| Net Investment Hedging [Member] \| Currency derivatives [Member]
Derivative Instruments [Abstract]
Net gain (loss) recognized in AOCI	0	0	8
Sales [Member] \| Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Currency derivatives [Member]
Derivative Instruments [Abstract]
Net gain (loss) reclassified from AOCI into earnings	6	(11)	40
Sales [Member] \| Not Designated as Hedging Instrument [Member] \| Currency derivatives [Member]
Derivative Instruments [Abstract]
Net gain (loss) recognized in earnings	6	(5)	2
Other Income [Member] \| Not Designated as Hedging Instrument [Member] \| Currency derivatives [Member]
Derivative Instruments [Abstract]
Net gain (loss) recognized in earnings	6	9	(5)
Foreign Currency Denominated Debt [Member] \| Designated as Hedging Instrument [Member] \| Net Investment Hedging [Member]
Non-Derivative Hedging Instruments [Abstract]
Net gain (loss) recognized in AOCI	45	(41)	2
Foreign Currency Denominated Debt [Member] \| Other Income [Member] \| Not Designated as Hedging Instrument [Member]
Non-Derivative Hedging Instruments [Abstract]
Net gain (loss) recognized in earnings	$ 9	$ (21)	$ 3

Derivative Instruments [Abstract]

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Non-Derivative Hedging Instruments [Abstract]

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No definition available.

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- Definition

Nonderivative, Gain (Loss) on Nonderivative, Net

+ References

No definition available.

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Nonderivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net

+ References

No definition available.

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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- Definition

Amount before tax 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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580

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-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

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