Commitments and Contingencies Guaranty (Details) - USD ($) $ in Millions |
Apr. 30, 2021 |
Apr. 30, 2020 |
|---|---|---|
| Concentration Risk [Line Items] | ||
| Accounts Receivable, after Allowance for Credit Loss, Current | $ 753 | $ 570 |
| Credit Concentration Risk [Member] | ||
| Concentration Risk [Line Items] | ||
| Guarantor Obligations, Maximum Exposure, Undiscounted | 9 | |
| Guarantee Obligations Current Exposure | 5 | |
| Accounts Receivable, after Allowance for Credit Loss, Current | $ 7 |