Pension and Other Postretirement Benefits (Changes in Funded Status of Benefit Plans Recognized in Other Comprehensive (Income) Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Pension Benefits [Member]
Amounts recognized in OCI
Net actuarial gain (loss)	$ (29)	$ 62	$ 69
Amortization reclassified to earnings:
Prior service cost (credit)	1	1	1
Net actuarial loss (gain)	38	35	27
Net amount recognized in OCI	10	98	97
Medical and Life Insurance Benefits [Member]
Amounts recognized in OCI
Net actuarial gain (loss)	2	5	1
Amortization reclassified to earnings:
Prior service cost (credit)	0	(2)	(3)
Net actuarial loss (gain)	0	1	1
Net amount recognized in OCI	$ 2	$ 4	$ (1)