Segment Information - Reconciliation, Interest Expense, Assets (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Segment Reporting [Line Items]
Net loss	$ 11,673	$ (12,901)	$ (7,711)	$ 10,715	$ (375)	$ (13,612)	$ (8,939)	$ (3,272)
Interest expense – other	(7,070)			(9,041)			(23,051)	(27,129)
Restructuring and impairment	(304)			(727)			(14,330)	(3,013)
Change in fair value of contingent consideration	0			(144)			(203)	(452)
Equity-based compensation	(4,006)			(2,459)			(8,947)	(6,717)
Transaction costs	(210)			(175)			(2,846)	(1,111)
Depreciation and amortization	(4,352)			(6,301)			(13,795)	(18,509)
Other expense, net	150			224			(1,031)	(853)
Net loss before income tax benefit	21,966			14,222			(6,500)	(5,175)
Interest expense – other	7,070			9,041			23,051	27,129
Assets	1,304,011						1,304,011		$ 1,403,825
Dealership
Segment Reporting [Line Items]
Interest expense – other	(7,070)			(9,041)			(23,051)	(27,129)
Net loss before income tax benefit	36,184			30,636
Interest expense – other	7,070			9,041			23,051	27,129
Assets	1,243,700						1,243,700		1,276,828
Distribution
Segment Reporting [Line Items]
Net loss	1,574
Interest expense – other	0			0			0	0
Interest expense – other	0			$ 0			0	$ 0
Assets	$ 60,311						$ 60,311		$ 126,997