Basis of Presentation and Accounting Policies - Revenue Recognition and Receivables (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity, including portion attributable to noncontrolling interest	$ 2,694.1	$ 1,346.8	$ 404.2	$ 1,617.5
Allowances for doubtful accounts	13.2	15.2
Allowance for certain customer returns, rebates and incentives	6.7	8.1
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity, including portion attributable to noncontrolling interest	$ 8,000.4	$ 7,139.8	$ 6,440.2	$ 6,198.1