Pension and Other Postretirement Benefits (Assumptions and SensItivity) (Details)
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12 Months Ended |
Apr. 30, 2021 |
Apr. 30, 2020 |
Apr. 30, 2019 |
| Pension Benefits [Member] |
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| Assumptions used in computing benefit plan obligations |
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|
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| Discount rate (percent) |
3.16%
|
3.28%
|
|
| Rate of salary increase (percent) |
4.00%
|
4.00%
|
|
| Interest crediting rate (percent) |
3.06%
|
3.07%
|
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| Assumptions used in computing benefit plan expense |
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|
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| Discount rate for service cost (percent) |
3.49%
|
4.17%
|
4.30%
|
| Discount rate for interest cost (percent) |
2.56%
|
3.57%
|
3.93%
|
| Rate of salary increase (percent) |
4.00%
|
4.00%
|
4.00%
|
| Interest crediting rate (percent) |
3.07%
|
3.07%
|
3.18%
|
| Expected return on plan assets (percent) |
6.50%
|
6.50%
|
6.50%
|
| Medical and Life Insurance Benefits [Member] |
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| Assumptions used in computing benefit plan obligations |
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|
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| Discount rate (percent) |
3.08%
|
3.17%
|
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| Assumptions used in computing benefit plan expense |
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| Discount rate for service cost (percent) |
3.59%
|
4.24%
|
4.34%
|
| Discount rate for interest cost (percent) |
2.47%
|
3.53%
|
3.90%
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| Assumed health care cost trend rates |
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|
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| Health care cost trend rate assumed for next year (percent) |
6.60%
|
6.90%
|
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| Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) (percent) |
4.50%
|
5.00%
|
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