Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Taxes [Line Items]
Income tax expense (benefit)	$ 4.6	$ 5.6	$ 4.6
Unrecognized tax benefits	0.0	0.0
Carryback claim refunded	0.8	(0.3)	$ (10.1)
Valuation allowance	$ 5.1	0.0
State
Income Taxes [Line Items]
Tax examination	2018
Net operating losses	$ 121.8
Net operating losses, expiration start year	2024
Valuation allowance	$ 5.1
U.S. federal
Income Taxes [Line Items]
Tax examination	2020
Cares Act
Income Taxes [Line Items]
Income taxes receivable	$ 39.0
Income tax expense (benefit)	10.1
Income tax credit related to employee retention	1.0	$ 3.3
Carryback claim refunded	$ 8.4