CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Interest income	$ 50,213			$ 47,579			$ 153,152	$ 128,942
Warehouse credit facility	6,251			5,522			22,708	12,279
Securitization debt	9,096			6,116			21,960	16,442
Total interest expense	15,347			11,638			44,668	28,721
Net interest income	34,866			35,941			108,484	100,221	$ 136,589	$ 82,163
Realized and unrealized losses, net of recoveries	38,346			37,258			87,894	76,173	122,541	(54,761)
Net interest income after losses and recoveries	(3,480)			(1,317)			20,590	24,048	14,048	71,883
Servicing Income	1,495			2,430			5,101	7,835
Warranties and GAP income (loss), net	3,917			146			(4,347)	3,732
CarStory revenue	2,890			2,998			8,782	9,392
Gain on debt extinguishment								19,640
Other income	2,419			2,057			8,344	8,160
Total noninterest income	10,721			7,631			17,880	48,759	75,126	208,983
Compensation and benefits	25,365			19,851			76,651	64,413
Professional fees	1,587			3,648			6,418	11,065
Software and IT costs	3,360			4,685			12,018	14,735
Depreciation and amortization	7,105			7,298			21,963	21,720
Interest expense on corporate debt	1,601			1,593			4,541	4,460
Impairment charges	2,407						5,159
Other expenses	3,436			3,861			12,853	13,631
Total expenses	44,861			40,936			139,603	130,024	173,629	179,965
Loss from continuing operations before provision for income taxes	(37,620)			(34,622)			(101,133)	(57,217)	(84,455)	100,901
Provision for income taxes from continuing operations	124			117			393	453	123	(19,680)
Net loss from continuing operations	(37,744)			(34,739)			(101,526)	(57,670)
Net loss from discontinued operations	(1,999)			(47,988)			(27,024)	(165,838)
Net loss	$ (39,743)	$ (21,188)	$ (67,617)	$ (82,727)	$ (66,039)	$ (74,741)	$ (128,550)	$ (223,508)	$ (364,611)	$ (450,464)
Net loss per share attributable to common stockholders, continuing operations, basic	$ (20.88)			$ (19.89)			$ (56.38)	$ (33.16)	$ (48.52)	$ 69.95
Net loss per share attributable to common stockholders, continuing operations, diluted	(20.88)			(19.89)			(56.38)	(33.16)	(48.52)	69.95
Net loss per share attributable to common stockholders, Discontinued operations, basic	(1.11)			(27.48)			(15.01)	(95.36)	(160.65)	(331.26)
Net loss per share attributable to common stockholders, Discontinued operations, diluted	(1.11)			(27.48)			(15.01)	(95.36)	(160.65)	(331.26)
Total net loss per share attributable to common stockholders, basic	(21.99)			(47.38)			(71.39)	(128.52)	(209.17)	(261.31)
Total net loss per share attributable to common stockholders, diluted	$ (21.99)			$ (47.38)			$ (71.39)	$ (128.52)	$ (209.17)	$ (261.31)
Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic	1,807,398			1,746,154			1,800,729	1,739,042	1,743,128	1,723,843
Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, diluted	1,807,398			1,746,154			1,800,729	1,739,042	1,743,128	1,723,843