Pension and Other Postretirement Benefits Sponsor Location (Details)	Apr. 30, 2021	Apr. 30, 2020
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Sponsor Location [Extensible List]	United States	United States
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Sponsor Location [Extensible List]	United States	United States