Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Inventory [Line Items]
Total inventories	$ 551,354	$ 539,793
New vessels
Inventory [Line Items]
Total inventories	414,114	395,300
Pre-owned vessels
Inventory [Line Items]
Total inventories	84,682	74,535
Parts and accessories, work in process
Inventory [Line Items]
Total inventories	$ 52,558	$ 69,958