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Company Background and Basis of Presentation - Additional Information (Detail)
12 Months Ended
Sep. 30, 2019
Store
State
Sep. 30, 2018
Sep. 30, 2017
Concentration Risk [Line Items]      
Number of retail locations | Store 59    
Number of states wherein retail locations are established | State 16    
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 36.00%    
Product Concentration Risk [Member] | Brunswick Sea Ray Boat [Member] | Brunswick [Member] | Sales [Member]      
Concentration Risk [Line Items]      
Revenue percentage from sale of boats 15.00%    
Product Concentration Risk [Member] | Brunswick Boston Whaler Boats [Member] | Brunswick [Member] | Sales [Member]      
Concentration Risk [Line Items]      
Revenue percentage from sale of boats 19.00%    
Product Concentration Risk [Member] | Azimut Benetti Groups and Yachts | Sales [Member]      
Concentration Risk [Line Items]      
Revenue percentage from sale of boats 9.00%    
Geographic Concentration Risk [Member] | Sales [Member] | Florida [Member]      
Concentration Risk [Line Items]      
Revenue percentage from sale of boats 54.00% 51.00% 55.00%