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, 2020	Apr. 30, 2019	Apr. 30, 2018
Total amounts presented in the accompanying condensed consolidated statements of operations for line items affected by the net gains (losses) shown above: [Abstract]
Sales	$ 4,306	$ 4,276	$ 4,201
Other income (expense), net	(11)	15	16
Foreign Currency Denominated Debt [Member]
Foreign currency-denominated debt designated as net investment hedge: [Abstract]
Net gain (loss) recognized in AOCI	22	45	(41)
Currency derivatives [Member]
Currency derivatives designated as cash flow hedges: [Abstract]
Net gain (loss) recognized in AOCI	61	69	(54)
Currency derivatives [Member] \| Sales [Member]
Currency derivatives designated as cash flow hedges: [Abstract]
Net gain (loss) reclassified from AOCI into earnings	23	6	(11)
Currency derivatives not designated as hedging instruments: [Abstract]
Net gain (loss) recognized in earnings	4	6	(5)
Currency derivatives [Member] \| Other Income (Expense), Net [Member]
Currency derivatives not designated as hedging instruments: [Abstract]
Net gain (loss) recognized in earnings	$ (14)	$ 6	$ 9

Currency derivatives not designated as hedging instruments: [Abstract]

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Derivative Instruments [Abstract]

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Total amounts presented in the accompanying condensed consolidated statements of operations for line items affected by the net gains (losses) shown above: [Abstract]

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

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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