BALANCE SHEETS COMPONENTS - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Machinery and equipment
Depreciation	$ 14,900,000	$ 2,100,000	$ 26,600,000	$ 5,400,000
Payroll tax liability	32,728,000		32,728,000		$ 0
Receivable from employees for non-income tax liability	27,400,000		27,400,000
Prepaid insurance	41,900,000		$ 41,900,000
Prepaid insurance, policy term (less than)			2 years
Payments for short-term insurance financing note			$ 16,819,000	0
Cash paid for interest			324,000	$ 21,000
Short-term insurance financing note	24,674,000		24,674,000		$ 980,000
Insurance Premiums Financed
Machinery and equipment
Prepaid insurance, down payment			9,400,000
Interest expense			400,000
Periodic payment amount			3,500,000
Payments for short-term insurance financing note	5,300,000		7,200,000
Cash paid for interest	100,000		100,000
Short-term insurance financing note	$ 24,700,000		$ 24,700,000
Insurance Premiums Financed | Minimum
Machinery and equipment
Interest rate	2.65%		2.65%
Insurance Premiums Financed | Maximum
Machinery and equipment
Interest rate	2.86%		2.86%