Summary of Significant Accounting Policies - Concentration Risks (Details) - Unionized Employees Concentration Risk	Apr. 30, 2021 employee
Number of Employees Hourly Workers
Accounting Policies [Line Items]
Concentration risk number of employees	8,400
concentration risk number of employees percentage	99.00%
Number of Employees Salaried Workers
Accounting Policies [Line Items]
Concentration risk number of employees	700
concentration risk number of employees percentage	13.00%