New Accounting Guidance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Oct. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liabilities	$ 393.4		$ 393.4
Right-of-use assets	351.1		351.1
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liabilities					$ 375.3
Right-of-use assets					$ 332.3
Other Non-Operating Income (Expense), Net | Accounting Standards Update 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excluded components recognized within earnings	$ 8.5		$ 17.4
Interest Expense | Accounting Standards Update 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excluded components recognized within earnings		$ 9.1		$ 17.4