Income Taxes (Tax Act) (Details) - USD ($) $ in Millions	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Tax Act [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	30.40%	35.00%
Income Tax Benefit from Reduction in Federal Statutory Income Tax Rate		$ 115
Tax Cuts and Jobs Act, Incomplete Accounting, Provisional Income Tax Expense (Benefit)			$ 43
Tax Cuts and Jobs Act, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense			91
Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)			$ (48)
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit)		4
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount	$ 11	$ 12

Income Tax Benefit from Reduction in Federal Statutory Income Tax Rate

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- Definition

Tax Act [Abstract]

+ References

No definition available.

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
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Amount of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to Tax Cuts and Jobs Act.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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Amount of reasonable estimate for income tax expense (benefit) for which accounting for tax effect for remeasurement of deferred tax from change in tax rate is incomplete pursuant to Tax Cuts and Jobs Act.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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Amount of reasonable estimate for income tax expense (benefit) for which accounting for tax effect is incomplete pursuant to Tax Cuts and Jobs Act.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of reasonable estimate for income tax expense for which accounting for tax effect from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated is incomplete pursuant to Tax Cuts and Jobs Act.

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Amount of income tax expense (benefit) for measurement period adjustment from accounting for tax effect pursuant to Tax Cuts and Jobs Act.

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