Inventories Narrative (Details) - USD ($)	Apr. 30, 2020	Jul. 31, 2019
Inventory
Inventory obsolescence reserve	$ 1,350,000	$ 704,000

Amount of valuation reserve for inventory.

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Name:	us-gaap_InventoryValuationReserves
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant