Pension and Other Postretirement Benefits (Funded Status Recorded on Accompanying Balance Sheets) (Details) - USD ($) $ in Millions	Apr. 30, 2022	Apr. 30, 2021
Funded status is recorded on the accompanying consolidated balance sheets
Accrued pension and other postretirement benefits	$ (183)	$ (219)
Pension Benefits [Member]
Funded status is recorded on the accompanying consolidated balance sheets
Other assets	46	4
Accounts payable and accrued expenses	(8)	(7)
Accrued pension and other postretirement benefits	(143)	(173)
Net liability	(105)	(176)
Accumulated other comprehensive income (loss), before tax:
Net actuarial gain (loss)	(201)	(298)
Prior service credit (cost)	(4)	(5)
Total	(205)	(303)
Medical and Life Insurance Benefits [Member]
Funded status is recorded on the accompanying consolidated balance sheets
Other assets	0	0
Accounts payable and accrued expenses	(3)	(3)
Accrued pension and other postretirement benefits	(40)	(46)
Net liability	(43)	(49)
Accumulated other comprehensive income (loss), before tax:
Net actuarial gain (loss)	(3)	(9)
Prior service credit (cost)	2	4
Total	$ (1)	$ (5)