Leases - Narrative (Details)	12 Months Ended
	Jul. 31, 2020 contract
Lessee, Lease, Description [Line Items]
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	cmd:LeaseLiabilityCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	cmd:LeaseLiabilityNoncurrent
Real Estate
Lessee, Lease, Description [Line Items]
Number of lease contracts	90
Number of renewal options	1
Real Estate | Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Real Estate | Maximum
Lessee, Lease, Description [Line Items]
Lease term	16 years