Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Inventory [Line Items]
Total inventories	$ 485,527	$ 539,793
New vessels
Inventory [Line Items]
Total inventories	362,131	395,300
Pre-owned vessels
Inventory [Line Items]
Total inventories	73,208	74,535
Parts and accessories, work in process
Inventory [Line Items]
Total inventories	$ 50,188	$ 69,958