Pension and Other Postretirement Benefits (Plans with ABO in Excess of Plan Assets) (Details) - USD ($)
$ in Millions |
Apr. 30, 2021 |
Apr. 30, 2020 |
Apr. 30, 2019 |
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
|
|
|
| Total, Plan Assets |
$ 836
|
$ 749
|
|
| Pension Plan [Member] |
|
|
|
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
|
|
|
| Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation |
(155)
|
(277)
|
|
| Defined Benefit Plan Pension Plans With Assets In Excess Of Accumulated Benefit Obligation Aggregate Accumulated Benefit Obligation |
(748)
|
(613)
|
|
| Defined Benefit Plan, Accumulated Benefit Obligation |
(903)
|
(890)
|
|
| Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets |
0
|
124
|
|
| Defined Benefit Plan Pension Plans With Assets In Excess Of Accumulated Benefit Obligation Aggregate Fair Value Of Plan Assets |
836
|
625
|
|
| Total, Plan Assets |
$ 836
|
$ 749
|
$ 754
|