Income Taxes - Schedule of Tax Attributes and Valuation Allowances (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Tax Benefit Amount
Capital loss carryforwards	$ 14.4	$ 13.0
Net operating loss carryforwards	60.8	85.2
State tax credit carryforward	9.2	$ 19.3
Subtotal	84.4
Other deferred tax assets	31.9
Total	116.3
Valuation Allowance
Tax credit carryforward	31.9
Subtotal	57.2
Total	89.1
Non-United States
Tax Benefit Amount
Net operating loss carryforward, subject to expiration	5.9
Net operating loss carryforward, not subject to expiration	46.1
Capital loss carryforwards	14.4
Valuation Allowance
Net operating loss carryforward, subject to expiration	2.5
Net operating loss carryforward, not subject to expiration	39.3
Non-United States capital loss carryforward	14.4
United States
Tax Benefit Amount
Net operating loss carryforward, subject to expiration	0.1
State tax credit carryforward	0.9
Valuation Allowance
Net operating loss carryforward, subject to expiration	0.0
Tax credit carryforward	0.0
State and Local
Tax Benefit Amount
Net operating loss carryforwards	8.7
State tax credit carryforward	8.3
Valuation Allowance
Net operating loss carryforward, subject to expiration	1.0
Tax credit carryforward	$ 0.0