Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) segment	Jun. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)
Segment Information [Abstract]
Number of reportable segments | segment			2
Revenue	$ 594,339	$ 568,900	$ 1,485,329	$ 1,347,299
Income (loss) from operations	60,080	87,544	135,506	178,262
Depreciation and amortization	6,584		19,126	10,816
Transaction costs	97	1,337	1,668	5,158
Change in fair value of contingent consideration	436	$ 3,118	763	$ 11,022
Total assets	1,771,317		1,771,317		$ 1,497,428
Eliminations
Segment Information [Abstract]
Revenue	(153)		(153)
Income (loss) from operations	(7)		(7)
Depreciation and amortization	0		0
Transaction costs	0		0
Change in fair value of contingent consideration	0		0
Total assets	(25)		(25)
Dealerships | Operating Segments
Segment Information [Abstract]
Revenue	543,312		1,348,433
Income (loss) from operations	59,699		137,938
Depreciation and amortization	2,768		7,706
Transaction costs	9		1,432
Change in fair value of contingent consideration	390		474
Total assets	1,368,783		1,368,783
Distribution | Operating Segments
Segment Information [Abstract]
Revenue	51,180		137,049
Income (loss) from operations	388		(2,425)
Depreciation and amortization	3,816		11,420
Transaction costs	88		236
Change in fair value of contingent consideration	46		289
Total assets	$ 402,559		$ 402,559