Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)
Segment Information [Abstract]
Number of reportable segments | segment			2
Revenue	$ 552,864	$ 542,441	$ 1,412,199	$ 1,394,775
Income (loss) from operations	30,379	39,999	44,677	60,325
Depreciation and amortization	6,301	5,785	18,509	16,255
Transaction costs	175	242	1,111	966
Change in fair value of contingent consideration	144	214	452	3,918
Restructuring and impairment	727	0	3,013	11,847
Total assets	1,540,429	1,635,880	1,540,429	1,635,880	$ 1,589,989
Eliminations
Segment Information [Abstract]
Revenue	(95)	(120)	(272)	(249)
Income (loss) from operations	(67)	(11)	(105)	(23)
Depreciation and amortization	0	0	0	0
Transaction costs	0	0	0	0
Change in fair value of contingent consideration	0	0	0	0
Restructuring and impairment	0	0	0	0
Total assets	(25)	(20)	(25)	(20)
Dealerships
Segment Information [Abstract]
Restructuring and impairment	500		1,600
Dealerships | Operating Segments
Segment Information [Abstract]
Revenue	513,371	497,793	1,307,463	1,279,609
Income (loss) from operations	31,573	38,804	52,362	60,691
Depreciation and amortization	3,690	3,276	10,776	9,244
Transaction costs	175	233	1,063	777
Change in fair value of contingent consideration	144	214	452	3,918
Restructuring and impairment	493	0	1,648	10,699
Total assets	1,318,156	1,396,048	1,318,156	1,396,048
Distribution
Segment Information [Abstract]
Restructuring and impairment	200		1,400
Distribution | Operating Segments
Segment Information [Abstract]
Revenue	39,588	44,768	105,008	115,415
Income (loss) from operations	(1,127)	1,206	(7,580)	(343)
Depreciation and amortization	2,611	2,509	7,733	7,011
Transaction costs	0	9	48	189
Change in fair value of contingent consideration	0	0	0	0
Restructuring and impairment	234	0	1,365	1,148
Total assets	$ 222,298	$ 239,852	$ 222,298	$ 239,852