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INCOME TAXES - EFFECTIVE INCOME TAX RATE (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Tax at statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal benefit	6.90%	12.20%	(1.40%)
Federal and state tax credits	5.30%	4.00%	3.90%
Stock-based compensation	(0.50%)	(0.80%)	2.10%
Net operating loss not benefitted	(6.90%)	(5.80%)	(4.30%)
Other	(0.30%)	(0.20%)	(5.50%)
Change in valuation allowance	(25.50%)	(30.40%)	(15.80%)
Effective tax rate	0.00%	0.00%	0.00%

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Effective income tax Rate reconciliation net operating loss not benefitted.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for share-based payment arrangement.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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