DEBT OBLIGATIONS - Narrative (Details)					1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Aug. 18, 2025 USD ($)	Aug. 21, 2024 USD ($) $ / shares shares	Jun. 17, 2024 USD ($)	Jan. 01, 2024 USD ($)	Jun. 30, 2025 USD ($)	Sep. 30, 2025 USD ($) instrument $ / shares shares	Sep. 30, 2024 USD ($) shares	Mar. 31, 2024 USD ($) $ / shares shares	Sep. 30, 2025 USD ($) instrument $ / shares shares	Sep. 30, 2024 USD ($) shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Aug. 15, 2025 USD ($)	Apr. 26, 2024 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) $ / shares shares
Debt Instrument [Line Items]
Warrants outstanding (in shares) | shares						18,581,679	14,695,691		18,581,679	14,695,691	14,615,703				15,309,547
Interest expense, debt						$ 3,361,000	$ 2,139,000		$ 12,662,000	$ 9,461,000
Amortization of debt discount and issue cost						772,000	393,000		2,973,000	1,914,000
Value of puttable warrants						0			0		$ 64,188,000
Debt instrument, unamortized discount and debt issuance costs						56,000			56,000		69,484,000
Debt issuance costs incurred						9,600,000			9,600,000
Repayments of long-term debt									140,000,000	57,322,000
Payment for debt prepayment premium									36,107,000	0
Loss on debt extinguishment						107,656,000	0		107,656,000	0
Warrants and rights outstanding											$ 64,188,000
Issuance of common stock								$ 5,531,000
Change in fair value of puttable warrants issued with debt						255,000	1,635,000		1,172,000	1,635,000
Share price (in dollars per share) | $ / shares											$ 22.34
2029 Senior Secured Term Loan Warrants
Debt Instrument [Line Items]
Warrants and rights outstanding													$ 65,400,000
Senior secured term loans | Prior Loan Agreement
Debt Instrument [Line Items]
Debt instrument, face amount																	$ 110,300,000
Debt instrument, interest rate, effective percentage																	14.50%
Debt discount														$ 500,000
Repayments of principal			$ 57,300,000
Repayments of interest			$ 400,000
Interest expense, debt										4,800,000
Amortization of debt discount and issue cost										1,300,000
Senior secured term loans | Prior Loan Agreement | Prior Loan Agreement Warrants
Debt Instrument [Line Items]
Warrants outstanding (in shares) | shares														662,338			162,338
Exercise price of warrants (in dollars per share) | $ / shares																	$ 14.50
Senior secured term loans | 2029 Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount		$ 100,000,000			$ 40,000,000	0			0		$ 100,000,000.0
Debt instrument, interest rate, effective percentage		52.60%			17.00%
Repayments of principal	$ 140,000,000
Repayments of interest	2,500,000
Interest expense, debt						3,100,000	1,800,000		11,900,000	1,800,000
Amortization of debt discount and issue cost						$ 700,000	300,000		$ 2,800,000	300,000
Long-term debt, term		5 years
Debt instrument, interest rate, stated percentage		12.90%			12.90%	12.90%			12.90%
Proceeds from issuance of long-term debt		$ 95,000,000			$ 36,900,000
Debt instrument, increase limit		100,000,000
Debt instrument, unamortized discount and debt issuance costs	71,600,000	$ 5,800,000
Debt issuance costs incurred					$ 3,000,000.0
Repayments of long-term debt	178,400,000
Payment for debt prepayment premium	36,000,000
Loss on debt extinguishment	107,700,000
Legal expenses	$ 100,000
Senior secured term loans | 2029 Senior Secured Term Loan | 2029 Senior Secured Term Loan Warrants
Debt Instrument [Line Items]
Number of securities called by warrants (in shares) | shares		3,795,564
Publicly traded float threshold for qualified IPO		$ 500,000,000
Offering proceeds threshold for qualified IPO		250,000,000
Value of puttable warrants		$ 59,500,000									$ 64,200,000
Senior secured term loans | 2029 Senior Secured Term Loan | 2029 Senior Secured Term Loan Warrants - Group 1
Debt Instrument [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares		$ 7.15
Number of securities called by warrants (in shares) | shares		2,277,338
Senior secured term loans | 2029 Senior Secured Term Loan | 2029 Senior Secured Term Loan Warrants - Group 2
Debt Instrument [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares		$ 8.55
Number of securities called by warrants (in shares) | shares		1,518,226
Convertible loans
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						9.50%			9.50%
Convertible loans | Convertible Loans
Debt Instrument [Line Items]
Interest expense, debt						$ 200,000	400,000		$ 600,000	2,800,000
Amortization of debt discount and issue cost						$ 100,000	100,000		$ 100,000	300,000
Convertible loans | Convertible Promissory Notes
Debt Instrument [Line Items]
Debt instrument, face amount																$ 56,200,000
Long-term debt, term																3 years
Debt instrument, interest rate, stated percentage																10.00%
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares						$ 16		$ 18.00	$ 16		$ 18.00					$ 18.00
Debt conversion, converted instrument, amount								$ 5,800,000			$ 50,400,000
Debt conversion, converted instrument, shares issued (in shares) | shares								322,222			2,797,222
Warrant modifications								$ 200,000
Issuance of common stock (in shares) | shares								5,557
Issuance of common stock								$ 100,000
Payment for debt inducement fee								$ 100,000
Convertible loans | Convertible Promissory Notes | Convertible Promissory Note Warrants
Debt Instrument [Line Items]
Warrants outstanding (in shares) | shares																100,000
Exercise price of warrants (in dollars per share) | $ / shares																$ 18.00
Warrants and rights outstanding																$ 200,000
Convertible loans | Convertible Loan
Debt Instrument [Line Items]
Debt instrument, face amount												$ 5,000,000.0
Long-term debt, term												5 years
Debt instrument, interest rate, stated percentage												9.50%
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares												$ 16.00
Beneficial conversion feature, percentage												75.00%
Beneficial conversion feature intrinsic value												$ 400,000
Increase in additional paid in capital from beneficial conversion feature				$ 100,000
Convertible loans | Convertible Loan | Convertible Loan Warrants
Debt Instrument [Line Items]
Warrants outstanding (in shares) | shares												1,807,847
Change in fair value of puttable warrants issued with debt												$ 600,000
Notes payable
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						8.00%			8.00%
Notes payable | Promissory Note
Debt Instrument [Line Items]
Debt instrument, face amount															$ 1,500,000
Interest expense, debt						$ 0	0		$ 100,000	100,000
Long-term debt, term															3 years
Debt instrument, interest rate, stated percentage															8.00%
Share price (in dollars per share) | $ / shares															$ 20.50
Notes payable | Promissory Note | Promissory Note Warrants
Debt Instrument [Line Items]
Warrants outstanding (in shares) | shares															7,408
Exercise price of warrants (in dollars per share) | $ / shares															$ 20.50
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Interest expense, debt						0	0		0	0
Long-term line of credit						$ 0			$ 0		$ 0
Line of Credit | Unsecured Revolving Lines Of Credit - MIAX Futures | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage						7.00%			7.00%		7.25%
Number of debt instruments held | instrument						2			2
Debt instrument, basis spread on variable rate									0.25%
Commitment fee percentage									0.40%
Line of Credit | Unsecured Revolving Lines Of Credit - MIAX Futures, Instrument One | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 6,000,000.0			$ 6,000,000.0
Line of Credit | Unsecured Revolving Lines Of Credit - MIAX Futures, Instrument Two | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 4,000,000.0			$ 4,000,000.0
Line of Credit | Secured Line Of Credit - MIAX Futures | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage						7.25%			7.25%		7.50%
Line of credit facility, maximum borrowing capacity						$ 40,000,000			$ 40,000,000
Commitment fee percentage									0.25%
Line of Credit | Unsecured Revolving Line Of Credit - Dorman Trading | Revolving Credit Facility
Debt Instrument [Line Items]
Interest expense, debt						0	$ 0		$ 0	$ 0
Line of credit facility, maximum borrowing capacity						10,000,000.0			$ 10,000,000.0
Debt instrument, basis spread on variable rate									3.00%
Long-term line of credit						$ 0			$ 0		$ 0