Income Taxes - Schedule of Tax Attributes and Valuation Allowances (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Tax Benefit Amount
Capital loss carryforwards	$ 16.0	$ 15.0
State tax credit carryforward	13.0	14.0
Net operating loss carryforwards	62.0	$ 70.0
Subtotal	91.0
Other deferred tax assets	60.0
Total	151.0
Valuation Allowance
Tax credit carryforward	60.0
Subtotal	69.0
Total	129.0
Non-United States
Tax Benefit Amount
Net operating loss carryforward, subject to expiration	5.0
Net operating loss carryforward, not subject to expiration	52.0
Capital loss carryforwards	16.0
Valuation Allowance
Net operating loss carryforward, subject to expiration	0.0
Net operating loss carryforward, not subject to expiration	52.0
Non-United States capital loss carryforward	16.0
State and Local
Tax Benefit Amount
State tax credit carryforward	13.0
Net operating loss carryforwards	5.0
Valuation Allowance
Net operating loss carryforward, subject to expiration	1.0
Tax credit carryforward	$ 0.0