Income Taxes - Schedule of Tax Attributes and Valuation Allowances (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Tax Benefit Amount
Capital loss carryforwards	$ 15.4	$ 14.4
State tax credit carryforward	14.2	9.2
Net operating loss carryforwards	69.6	$ 60.8
Subtotal	99.2
Other deferred tax assets	29.3
Total	128.5
Valuation Allowance
Tax credit carryforward	29.3
Subtotal	68.2
Total	97.5
Non-United States
Tax Benefit Amount
Net operating loss carryforward, subject to expiration	10.7
Net operating loss carryforward, not subject to expiration	51.8
Capital loss carryforwards	15.4
State tax credit carryforward	1.9
Valuation Allowance
Net operating loss carryforward, subject to expiration	2.1
Net operating loss carryforward, not subject to expiration	47.9
Non-United States capital loss carryforward	15.4
Tax credit carryforward	0.0
United States
Tax Benefit Amount
State tax credit carryforward	0.3
Valuation Allowance
Tax credit carryforward	0.0
State and Local
Tax Benefit Amount
State tax credit carryforward	12.0
Net operating loss carryforwards	7.1
Valuation Allowance
Net operating loss carryforward, subject to expiration	2.8
Tax credit carryforward	$ 0.0