Segment Information - Reconciliation between Reportable Segment Adjusted EBITDA to Consolidated Loss from continuing Operations Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Adjusted EBITDA by Segment
Total	$ (25,534)	$ (25,959)	$ (65,229)	$ (52,576)
Interest expense on corporate debt	(1,601)	(1,593)	(4,541)	(4,460)
Interest income on cash and cash equivalents	1,035	2,007	3,221	7,026
Depreciation and amortization	(7,105)	(7,298)	(21,963)	(21,720)
Stock compensation expense	(1,244)	(1,779)	(5,014)	(5,126)
Gain on debt extinguishment				19,640
Severance	(763)		(2,448)
Impairment charges	(2,407)		(5,159)
Loss from continuing operations before provision for income taxes	(37,620)	(34,622)	(101,133)	(57,217)	$ (84,455)	$ 100,901
Corporate
Adjusted EBITDA by Segment
Total	(11,205)	(16,715)	(38,858)	(40,358)
Interest expense on corporate debt	(920)	(1,053)	(2,760)	(3,287)
Gain on debt extinguishment				19,640
UACC | Operating Segments
Adjusted EBITDA by Segment
Total	(14,119)	(9,780)	(27,091)	(13,956)
Interest expense on corporate debt	(681)	(540)	(1,781)	(1,173)
Depreciation and amortization	(5,505)	(5,689)	(17,156)	(16,898)
Impairment charges	(2,407)		(5,159)
CarStory | Operating Segments
Adjusted EBITDA by Segment
Total	(210)	536	720	1,738
Depreciation and amortization	$ (1,600)	$ (1,609)	$ (4,807)	$ (4,822)