Acquisitions (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022 USD ($) Location	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) Location	Mar. 31, 2021 USD ($)	Dec. 01, 2021 Location	Oct. 02, 2021 Location	Sep. 30, 2021 USD ($)
Acquisition [Abstract]
Cash paid for acquisition			$ 288,900
Note payable to seller			1,100
Payment of contingent consideration	$ 15,300		15,300
Issuance of shares of Class A common stock			6,800
Minimum payout due of contingent consideration	5,900		5,900
Maximum payout due of contingent consideration	24,700		24,700
Summary of Assets Acquired and Liabilities Assumed [Abstract]
Goodwill	313,460		313,460				$ 168,491
Consideration transferred	312,200		312,200
Revenue	442,127	$ 329,611	778,399	$ 543,694
Income before income tax expense	55,135	37,142	83,510	51,428
Costs related to acquisition	700	400	3,700	600
Unaudited Pro Forma Results of Operations [Abstract]
Pro forma revenue	443,901	413,583	821,412	734,457
Pro forma net income	$ 42,583	$ 40,468	$ 66,257	$ 58,019
Notes Payable [Member]
Acquisition [Abstract]
Interest rate	4.00%		4.00%
Naples Boat Mart [Member]
Acquisition [Abstract]
Number of stores | Location						1
Norfolk Marine [Member]
Acquisition [Abstract]
Number of stores | Location					1
T-H Marine [Member]
Summary of Assets Acquired and Liabilities Assumed [Abstract]
Accounts receivable	$ 8,955		$ 8,955
Inventories	19,856		19,856
Prepaid expenses	1,547		1,547
Property and equipment	3,896		3,896
Operating lease right-of-use assets	5,960		5,960
Identifiable intangible assets	105,500		105,500
Goodwill	51,694		51,694
Accounts payable	(3,876)		(3,876)
Accrued expenses	(1,697)		(1,697)
Customer deposits	(394)		(394)
Operating lease liabilities	(5,960)		(5,960)
Aggregate acquisition date fair value	185,481		185,481
Consideration transferred	185,481		185,481
Fair value of non-controlling interests	$ 0		$ 0
Quality Boats [Member]
Acquisition [Abstract]
Number of stores | Location	3		3
Percentage of economic interest retained by sellers	20.00%		20.00%
Percentage of remaining economic interest	20.00%		20.00%
Summary of Assets Acquired and Liabilities Assumed [Abstract]
Accounts receivable	$ 0		$ 0
Inventories	5,937		5,937
Prepaid expenses	54		54
Property and equipment	803		803
Operating lease right-of-use assets	428		428
Identifiable intangible assets	31,700		31,700
Goodwill	78,682		78,682
Accounts payable	0		0
Accrued expenses	0		0
Customer deposits	(5,047)		(5,047)
Operating lease liabilities	(428)		(428)
Aggregate acquisition date fair value	112,129		112,129
Consideration transferred	92,818		92,818
Fair value of non-controlling interests	19,311		19,311
Other Acquisitions [Member]
Summary of Assets Acquired and Liabilities Assumed [Abstract]
Accounts receivable	1,122		1,122
Inventories	9,618		9,618
Prepaid expenses	370		370
Property and equipment	1,227		1,227
Operating lease right-of-use assets	218		218
Identifiable intangible assets	11,276		11,276
Goodwill	14,594		14,594
Accounts payable	(471)		(471)
Accrued expenses	(553)		(553)
Customer deposits	(3,307)		(3,307)
Operating lease liabilities	(218)		(218)
Aggregate acquisition date fair value	33,876		33,876
Consideration transferred	33,876		33,876
Fair value of non-controlling interests	0		0
Total Acquisitions [Member]
Summary of Assets Acquired and Liabilities Assumed [Abstract]
Accounts receivable	10,077		10,077
Inventories	35,411		35,411
Prepaid expenses	1,971		1,971
Property and equipment	5,926		5,926
Operating lease right-of-use assets	6,606		6,606
Identifiable intangible assets	148,476		148,476
Goodwill	144,970		144,970
Accounts payable	(4,347)		(4,347)
Accrued expenses	(2,250)		(2,250)
Customer deposits	(8,748)		(8,748)
Operating lease liabilities	(6,606)		(6,606)
Aggregate acquisition date fair value	331,486		331,486
Consideration transferred	312,175		312,175
Fair value of non-controlling interests	19,311		19,311
Revenue	72,400		86,600
Income before income tax expense	$ 12,200		$ 13,300