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Basis of Presentation - Additional Information (Detail)	9 Months Ended
	Jun. 30, 2018 Dealer Operations
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Previously independent recreational boat dealers | Dealer	5
Recreational boat dealers | Dealer	28
Boat brokerage operations | Operations	2
Full-service yacht repair operations | Operations	2

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Boat brokerage operations number.

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Full service yacht repair operations number.

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Independent recreational boat dealers in number.

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Recreational boat dealers in number.

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