Acquisitions and Dispositions - Narrative (Details) $ in Thousands			12 Months Ended
	Oct. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) property renewal_option	Sep. 30, 2024 USD ($) location	Sep. 30, 2023 USD ($) property renewal_option	Sep. 30, 2022 USD ($)	Sep. 01, 2023 location	Apr. 01, 2022 state location	Dec. 31, 2021 location	Dec. 01, 2021 location	Oct. 01, 2021 location
Business Acquisition [Line Items]
Number of retail locations | location			96
Consideration transferred		$ 42,000		$ 42,000	$ 490,600
Cash paid for acquisition			$ 5,712	28,882	459,540
Noncash acquisition purchase price funded by affiliate financing			0	10,600	0
Contingent consideration, liability		2,600		2,600	15,300
Revenue from contract with customer			1,772,630	1,936,310	1,744,822
Net (loss) income before income tax expense			(6,333)	(42,523)	195,836
Costs related to acquisition			100	1,200	7,500
Business combination, consideration transferred, liabilities incurred					1,100
Issuance of shares of Class A common stock					14,600
Minimum payout due of contingent consideration					5,900
Maximum payout due of contingent consideration					24,700
Goodwill expected to be deductible for tax purposes		15,900	$ 0	$ 15,900	$ 173,200
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Roscioli Yachting Center [Member]
Business Acquisition [Line Items]
Term of contract			10 years
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Roscioli Yachting Center [Member] | Dealerships
Business Acquisition [Line Items]
Gain (loss) on sale and leaseback transaction		$ 0
Notes Payable
Business Acquisition [Line Items]
Debt instrument, interest rate, stated percentage					4.00%
Harbor Pointe Marina
Business Acquisition [Line Items]
Number of retail locations | location						1
Harbor View Marine
Business Acquisition [Line Items]
Number of retail locations | property		2		2
Gain (loss) on sale and leaseback transaction				$ 0
Term of contract		15 years		15 years
Number of lease renewal options | renewal_option		2		2
Renewal term		5 years		5 years
Total Acquisitions
Business Acquisition [Line Items]
Consideration transferred		$ 42,032		$ 42,032	$ 492,444
Revenue from contract with customer			$ 7,000	60,900	275,300
Net (loss) income before income tax expense			$ 200	$ 6,300	41,100
Naples Boat Mart
Business Acquisition [Line Items]
Number of retail locations | location										1
Norfolk Marine
Business Acquisition [Line Items]
Number of retail locations | location									1
Quality Boats
Business Acquisition [Line Items]
Number of retail locations | location								3
Consideration transferred					92,811
Percentage of economic interest retained by sellers			80.00%					20.00%
Denison Yachting
Business Acquisition [Line Items]
Consideration transferred					$ 44,995
Number of retail locations | location							20
Number of states | state							7
Quality Assets And Operations, LLC
Business Acquisition [Line Items]
Company owns economic interest	20.00%
Economic interest percentage	100.00%
Business Combination, Consideration Transferred	$ 18,800