Restructuring and Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
2025 Impairment
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	$ 149,700
2025 Impairment | Dealerships
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	50,000
2025 Impairment | Distribution
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	99,700
2025 Impairment | Restructuring and impairment
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	148,100
2025 Impairment | New boat cost of sales
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	1,600
2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring	$ 0	$ 15,300	$ 0
2024 Restructuring | Dealerships
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring		13,000
2024 Restructuring | Distribution
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring		2,300
2024 Restructuring | Restructuring and impairment
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring		12,400
2024 Restructuring | New boat cost of sales
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring		1,800
2024 Restructuring | Service, Parts and Other Cost of Sales
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring		$ 1,100
2023 Impairment
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring			147,400
2023 Impairment | Dealerships
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring			6,500
2023 Impairment | Distribution
Restructuring Cost and Reserve [Line Items]
Impairment and restructuring			$ 140,900