Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jul. 31, 2018	Apr. 30, 2019	Apr. 30, 2018
Expected Tax Rate on Ordinary Income	21.10%
Effective Income Tax Rate Reconciliation, Percent	17.40%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			30.40%
Income Tax Benefit from Reduction in Federal Statutory Income Tax Rate	$ 27
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, Incomplete Accounting, Measurement Period Adjustment, Provisional Income Tax Expense (Benefit)	6
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount	$ 2
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%