Basis of Presentation - Additional Information (Detail)	9 Months Ended
Jun. 30, 2021 Segment Dealer Operations Manufacturer
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of reportable segments \| Segment	2
Recreational boat dealers \| Dealer	30
Boat brokerage operations	4
Full-service yacht repair operations	2
Manufacturer \| Manufacturer	1

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration