COMMITMENTS AND CONTINGENCIES (Details)		1 Months Ended	3 Months Ended			9 Months Ended
	Sep. 03, 2020 USD ($) shares	Feb. 28, 2019 USD ($) a	Jun. 30, 2020 USD ($)	Sep. 30, 2019 shares	[1]	Sep. 30, 2020 shares	[2]	Sep. 30, 2019 shares	[3]
Other Commitments [Line Items]
Professional fees			$ 3,000,000.0
General Motors
Other Commitments [Line Items]
Lock-up restriction period	4 years 6 months
Standstill restriction period	3 years
Standstill restriction period, ownership threshold minimum	10.00%
Maximum | General Motors
Other Commitments [Line Items]
Capital expense reimbursement	$ 700,000,000
Common Stock
Other Commitments [Line Items]
Issuance of common stock (in sharess) | shares				5,132,291		9,443,353		5,132,291
Common Stock | General Motors
Other Commitments [Line Items]
Issuance of common stock (in sharess) | shares	47,698,545
In-kind consideration	$ 2,000,000,000
Coolidge, Arizona
Other Commitments [Line Items]
Area of land | a		430
Manufacturing Facility Commitment
Other Commitments [Line Items]
Construction completion, maximum extension period (in years)		2 years
Construction completion period (in years)		5 years
Security deposit payable		$ 4,000,000.0
Construction completion deadline monthly extension fee		$ 200,000

[1] Issuance of Series D redeemable convertible preferred stock has been retroactively restated to give effect to the recapitalization transaction.

[2] Issuance of Series D redeemable convertible preferred stock has been retroactively restated to give effect to the recapitalization transaction.

[3] Issuance of Series D redeemable convertible preferred stock has been retroactively restated to give effect to the recapitalization transaction.