Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Inventory [Line Items]
Total inventories	$ 598,567	$ 609,616
New vessels
Inventory [Line Items]
Total inventories	449,004	471,147
Pre-owned vessels
Inventory [Line Items]
Total inventories	77,145	61,627
Work in process, parts and accessories
Inventory [Line Items]
Total inventories	$ 72,418	$ 76,842