Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Inventory [Line Items]
Total inventories, net	$ 687,477	$ 609,616
New vessels
Inventory [Line Items]
Total inventories, net	536,126	471,147
Pre-owned vessels
Inventory [Line Items]
Total inventories, net	78,425	61,627
Work in process, parts and accessories
Inventory [Line Items]
Total inventories, net	$ 72,926	$ 76,842