BALANCE SHEET DETAILS - Schedule of Inventories (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Finished goods at customer sites	$ 0.5	$ 0.6

Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date, of merchandise or goods at customer sites for which the customer has taken possession, but based on contractual terms, title has not yet passed to the customer.

No definition available.

Name:	utsi_InventoryFinishedGoodsNetOfReservesAtCustomerSites
Namespace Prefix:	utsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant