CONVERTIBLE PREFERRED SHARES AND SHAREHOLDERS' DEFICIT - Dividends (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Noncumulative dividends rate (as a percent)	8.00%
Dividend declared	$ 0	$ 0
Series A
Class of Stock [Line Items]
Noncumulative dividends at an annual rate (in dollar per share)	$ 0.03
Series B
Class of Stock [Line Items]
Noncumulative dividends at an annual rate (in dollar per share)	0.09
Series C
Class of Stock [Line Items]
Noncumulative dividends at an annual rate (in dollar per share)	$ 0.19

Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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(24))
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant