Pension and Other Postretirement Benefits (Schedule of Components of Pension Expense) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Pension Expense
Service cost	$ 26	$ 26	$ 24
Interest cost	22	25	31
Expected return on assets	(45)	(46)	(46)
Amortization of prior service cost (credit)	1	1	1
Amortization of net actuarial loss (gain)	23	27	19
Settlement charge	12	0	1
Net cost	$ 39	$ 33	$ 30