INVENTORIES Schedule of Service Parts Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Inventory Disclosure [Abstract]
Finished goods	$ 17,924	$ 15,845
Component parts	5,287	4,657
Total service parts inventories	$ 23,211	$ 20,502

Carrying amount of completed service parts merchandise or goods expected to be sold within one year or operating cycle, if longer.

No definition available.

Name:	qtm_ServicePartsInventoriesFinishedGoods
Namespace Prefix:	qtm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant