Pension and Other Postretirement Benefits (Assumptions and SensItivity) (Details)	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Pension Benefits [Member]
Assumptions used in computing benefit plan obligations
Discount rate (percent)	4.36%	3.16%
Rate of salary increase (percent)	4.00%	4.00%
Interest crediting rate (percent)	3.06%	3.06%
Assumptions used in computing benefit plan expense
Discount rate for service cost (percent)	3.36%	3.49%	4.17%
Discount rate for interest cost (percent)	2.34%	2.56%	3.57%
Rate of salary increase (percent)	4.00%	4.00%	4.00%
Interest crediting rate (percent)	3.06%	3.07%	3.07%
Expected return on plan assets (percent)	6.25%	6.50%	6.50%
Medical and Life Insurance Benefits [Member]
Assumptions used in computing benefit plan obligations
Discount rate (percent)	4.33%	3.08%
Assumptions used in computing benefit plan expense
Discount rate for service cost (percent)	3.49%	3.59%	4.24%
Discount rate for interest cost (percent)	2.27%	2.47%	3.53%
Assumed health care cost trend rates
Health care cost trend rate assumed for next year (percent)	6.10%	6.60%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) (percent)	4.50%	4.50%