SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Contract Costs (Details) $ in Thousands	9 Months Ended
Sep. 30, 2021 USD ($)
Movement In Capitalized Contract Costs, Net [Roll Forward]
Balance as of January 1, 2021	$ 549
Additions to deferred contract costs	378
Amortization of deferred contract costs	(70)
Balance as of June 30, 2021	$ 857

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123353750&loc=SL49131252-203054

Name:	us-gaap_CapitalizedContractCostNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant