Taxes on Income - Narrative - Valuation Allowance (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Valuation Allowance [Line Items]
Valuation allowance	$ 319.3	$ 320.6
Capital loss [Member]
Valuation Allowance [Line Items]
Valuation allowance	37.8
Domestic, State and Foreign Jurisdiction [Member] | Operating loss carryforward [Member]
Valuation Allowance [Line Items]
Valuation allowance	195.1
Foreign Tax Authority [Member] | Tax credit carryforward [Member]
Valuation Allowance [Line Items]
Valuation allowance	73.1
Foreign Tax Authority [Member] | Other tax carryforward [Member]
Valuation Allowance [Line Items]
Valuation allowance	$ 13.3