Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024
Inventory [Line Items]
Total inventories	$ 517,093	$ 590,838
New vessels
Inventory [Line Items]
Total inventories	382,094	442,834
Pre-owned vessels
Inventory [Line Items]
Total inventories	67,001	79,234
Work in process, parts and accessories
Inventory [Line Items]
Total inventories	$ 67,998	$ 68,770