Company Background and Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2021 Store State	Sep. 30, 2020	Sep. 30, 2019
Concentration Risk [Line Items]
Number of retail locations | Store	77
Number of states wherein retail locations are established | State	21
Product Concentration Risk [Member] | Sales [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	100.00%	100.00%	100.00%
Product Concentration Risk [Member] | Brunswick [Member] | Sales [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	27.00%
Product Concentration Risk [Member] | Brunswick Sea Ray Boat [Member] | Brunswick [Member] | Sales [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	11.00%
Product Concentration Risk [Member] | Brunswick Boston Whaler Boats [Member] | Brunswick [Member] | Sales [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	13.00%
Product Concentration Risk [Member] | Azimut Benetti Groups and Yachts | Sales [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	10.00%
Geographic Concentration Risk [Member] | Sales [Member] | Florida [Member]
Concentration Risk [Line Items]
Revenue percentage from sale of boats	50.00%	54.00%	54.00%