Pension and Other Postretirement Benefits (Schedule of Components of Pension Expense) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Pension Expense
Service cost	$ 20	$ 26	$ 26
Interest cost	32	22	25
Expected return on assets	(43)	(45)	(46)
Amortization of prior service cost (credit)	1	1	1
Amortization of net actuarial loss (gain)	9	23	27
Settlement charge	29	12	0
Net cost	$ 48	$ 39	$ 33