INVENTORIES Schedule of Service Parts Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Mar. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Finished goods	$ 13,735	$ 13,437
Component parts	5,200	5,633
Total service inventories	$ 18,935	$ 19,070

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