Pension and Other Postretirement Benefits (Change in Benefit Obligation) (Details) - USD ($) $ in Millions		12 Months Ended
		Apr. 30, 2024	Apr. 30, 2023	Apr. 30, 2022
Pension Benefits [Member]
Changes in present value of pension and other postretirement benefits
Obligation at beginning of year		$ 731	$ 846
Service cost		18	20	$ 26
Interest cost		34	32	22
Net actuarial loss (gain)1	[1]	(61)	(21)
Retiree contributions		0	0
Benefits paid		(44)	(146)
Obligation at end of year		679	731	846
Medical and Life Insurance Benefits [Member]
Changes in present value of pension and other postretirement benefits
Obligation at beginning of year		40	43
Service cost		0	1	1
Interest cost		2	1	1
Net actuarial loss (gain)1	[1]	(3)	(2)
Retiree contributions		3	2
Benefits paid		(6)	(5)
Obligation at end of year		$ 36	$ 40	$ 43

[1] The net actuarial loss (gain) during each year was primarily attributable to changes in discount rates