Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Jul. 31, 2025
Income Taxes [Line Items]
Exceeded percent of total income taxes paid (net of refunds)	5.00%
Income tax benefit	$ (25.3)	$ (30.1)	$ (4.6)
Percentage of bonus depreciation on interest expense and research and development expenditure				100.00%
Percentage of bonus depreciation on capital investments and expansion				100.00%
Unrecognized tax benefits	$ 0.0	$ 0.0
U.S. corporate income tax rate	21.00%	21.00%	21.00%
Interest expense carryforward	$ 2.1	$ 1.2	$ 5.1
Increase to the valuation allowance	2.1
Valuation allowance	9.3	$ 6.3
Operating loss carryforwards, Valuation allowance	0.9
Canadian
Income Taxes [Line Items]
Net operating losses	$ 2.8
State
Income Taxes [Line Items]
Tax examination	2019
Net operating losses	$ 95.2
Net operating losses, expiration start year	2026
Interest expense carryforward	$ 149.5
Valuation allowance	$ 8.4
U.S. federal
Income Taxes [Line Items]
Tax examination	2020
Net operating losses	$ 3.0
Interest expense carryforward	111.0
Cares Act
Income Taxes [Line Items]
Income taxes receivable	39.0
Income tax benefit	10.1
Income tax credit related to employee retention	3.3
Income tax credit related to employee retention outstanding amount	0.4
Carryback claim refunded	$ 8.4