FAIR VALUE MEASUREMENT - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Notes Payable, Current	$ 4,086	$ 4,301
Seven Point Five Percentage Convertible Notes [Member]
Notes Payable, Current	57,900
Fair Value, Inputs, Level 3 [Member] \| Seven Point Five Percentage Convertible Notes [Member]
Convertible Debt, Fair Value Disclosures	58,700
Notes Payable, Current	$ 57,900

Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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