CONTINGENT FORWARD CONTRACTS - Series E convertible preferred shares (Details) - Series E convertible preferred shares	Dec. 31, 2020 Y	Sep. 22, 2020
Expected term
Derivative [Line Items]
Measurement input	0.25
Current price/ Price per share
Derivative [Line Items]
Measurement input	3.82	2.99
Present value factor
Derivative [Line Items]
Measurement input	1.0000	0.9999
Estimated probability of satisfying milestones
Derivative [Line Items]
Measurement input	100	95

Value of input used to measure derivative liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_DerivativeLiabilityMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant