Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2023 USD ($) segment	Mar. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)
Segment Information [Abstract]
Number of reportable segments | segment			2
Revenue	$ 524,331	$ 442,127	$ 890,990	$ 778,399
Income (loss) from operations	48,890	59,389	75,426	90,718
Depreciation and amortization	6,360		12,542	6,541
Transaction costs	241	776	1,571	3,821
Change in fair value of contingent consideration	1,736	$ 2,158	327	$ 7,904
Total assets	1,770,451		1,770,451		$ 1,497,428
Dealerships
Segment Information [Abstract]
Revenue	478,348		805,121
Income (loss) from operations	48,386		78,239
Depreciation and amortization	2,564		4,938
Transaction costs	241		1,423
Change in fair value of contingent consideration	1,626		83
Total assets	1,361,097		1,361,097
Distribution
Segment Information [Abstract]
Revenue	45,983		85,869
Income (loss) from operations	504		(2,813)
Depreciation and amortization	3,796		7,604
Transaction costs	0		148
Change in fair value of contingent consideration	110		244
Total assets	$ 409,354		$ 409,354