Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Component of Inventory [Abstract]
Inventories	$ 116,873	$ 150,124
New Vessels [Member]
Component of Inventory [Abstract]
Inventories	88,651	120,012
Pre-owned Vessels [Member]
Component of Inventory [Abstract]
Inventories	16,317	21,262
Work in Process, Parts and Accessories [Member]
Component of Inventory [Abstract]
Inventories	$ 11,905	$ 8,850

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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