SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) dealer segment business_unit	Dec. 31, 2023 USD ($) segment dealer	Dec. 12, 2023 USD ($)	Jun. 30, 2023 USD ($)	Apr. 30, 2023 USD ($)	Apr. 11, 2023 USD ($)	Jun. 30, 2022 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Number of business components | business_unit	2
Number of dealers the company sold FCEV & BEV trucks to | dealer	9	10
Dealers individually representing sales in excess of 10% of total revenue | dealer	3	4
Cash and cash equivalents	$ 104,302,000	$ 464,715,000
Cash equivalents, at carrying value	19,100,000	29,800,000
Restricted cash	$ 17,300,000	29,300,000
Derivative liability		$ 8,871,000
Number of reportable segments | segment	1	1
Number of operating segments | segment	1	1
Goodwill, impairment loss	$ 5,238,000	$ 0
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]	Impairment expense
Impairment of indefinite-lived intangible assets	$ 47,200,000	0
Tangible asset impairment charges	254,200,000
Impairment	77,097,000
Operating lease right of use assets	200,000
Contract with customer, asset, allowance for credit loss	$ 7,400,000	700,000
Contract with customer, funded by HVIP voucher, payment terms	180 days
Recall campaign accrual	$ 57,400,000	65,800,000
Incurred recall campaign cost	44,300,000	3,000,000
Advertising expense	1,600,000	2,000,000.0
Foreign currency gain (loss)	2,000,000	(2,200,000)
S-WAY Product and Platform license
Restricted Cash and Cash Equivalents Items [Line Items]
Impairment	$ 29,916,000
Minimum
Restricted Cash and Cash Equivalents Items [Line Items]
Interest rate, stated percentage	6.64%
Contract with customer, payment terms	5 days
Warranty period	2 years
Maximum
Restricted Cash and Cash Equivalents Items [Line Items]
Interest rate, stated percentage	6.99%
Contract with customer, payment terms	30 days
Warranty period	5 years
June 2022 Toggle Convertible Notes | Convertible Notes Payable
Restricted Cash and Cash Equivalents Items [Line Items]
Principal amount	$ 43,282,000	123,478,000		$ 100,000,000.0		$ 100,000,000.0	$ 200,000,000.0
Interest rate, stated percentage							8.00%
Paid-in-kind interest rate							11.00%
April 2023 Toggle Convertible Notes | Convertible Notes Payable
Restricted Cash and Cash Equivalents Items [Line Items]
Principal amount				100,000,000.0	$ 100,000,000.0
Interest rate, stated percentage					8.00%
Paid-in-kind interest rate					11.00%
Derivative liability				21,200,000
June 2023 Toggle Convertible Notes | Convertible Notes Payable
Restricted Cash and Cash Equivalents Items [Line Items]
Principal amount	12,395,000	11,460,000		$ 11,000,000.0
Interest rate, stated percentage				8.00%
Paid-in-kind interest rate				8.00%
8.25% Convertible Notes | Convertible Notes Payable
Restricted Cash and Cash Equivalents Items [Line Items]
Principal amount	$ 1,758,000	$ 21,558,000	$ 175,000,000
Interest rate, stated percentage	8.25%		8.25%
Derivative liability			$ 47,300,000
Convertible Senior PIK Toggle Notes | Convertible Notes Payable
Restricted Cash and Cash Equivalents Items [Line Items]
Principal amount						$ 100,000,000.0
Interest rate, stated percentage						8.00%
Paid-in-kind interest rate						11.00%