Derivative Financial Instruments and Hedging Activities Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Apr. 30, 2021	Apr. 30, 2020
Offsetting Assets and Liabilities [Line Items]
Gross Amount of Derivative Assets	$ 10	$ 79
Gross Amount of Derivative Liabilities Offset Against Derivative Assets in Balance Sheet	(7)	(1)
Net Amount of Derivative Assets Presented in Balance Sheet	3	78
Gross Amount of Derivative Liabilities Not Offset Against Derivative Assets in Balance Sheet	(1)	0
Net Amount of Derivative Assets	2	78
Gross Amount of Derivative Liabilities	(38)	(3)
Gross Amount of Derivative Assets Offset Against Derivative Liabilities in Balance Sheet	7	1
Net Amount of Derivative Liabilities Presented in Balance Sheet	(31)	(2)
Gross Amount of Derivative Assets Not Offset Against Derivative Liabilities in Balance Sheet	1	0
Net Amount of Derivative Liabilities	$ (30)	$ (2)