Leases ROU Assets and Liabilities (Details) - USD ($) $ in Millions	Apr. 30, 2021	Apr. 30, 2020
Leases [Abstract]
Right-of-use assets	$ 67	$ 51
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Lease Liabilities:
Current	$ 20	$ 16
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndOtherAccruedLiabilitiesCurrent
Non-current	$ 49	$ 37
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total	$ 69	$ 53
Weighted-average discount rate	1.90%	3.00%
Weighted-average remaining term	5 years 3 months 18 days	5 years 2 months 12 days