INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016
Income Tax Contingency [Line Items]
Provision for (benefit from) income taxes	$ 49,000	$ (188,000)	$ 23,000
Effective income tax rate	0.00%	0.00%	0.00%
Undistributed earnings of foreign subsidiaries	$ 0	$ 0
Valuation allowance	672,898,000	360,573,000
Increase valuation allowance for deferred tax assets	312,300,000	185,800,000
Operating loss carryforwards, amount nullified by ownership change					$ 12,000,000
Tax credit carryforward, amount nullified by ownership change					15,000,000
Net tax credit amount nullified by ownership change					$ 3,000,000
Unrecognized tax benefits	72,330,000	42,894,000	$ 20,635,000	$ 11,647,000
Unrecognized tax benefits that would impact effective tax rate	500,000	$ 2,600,000	$ 2,600,000
Unrecognized tax benefits, interest on income taxes accrued	60,000
Unrecognized tax benefits, income tax penalties accrued	7,000
Federal
Income Tax Contingency [Line Items]
Operating loss carryforwards	2,003,000,000
Federal | Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	80,500,000
State
Income Tax Contingency [Line Items]
Operating loss carryforwards	922,700,000
State | Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	63,100,000
Foreign
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 2,000,000.0