New Accounting Guidance (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2019	Oct. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flow operating activities	$ 2,969.9	$ 2,547.2	$ 2,528.4
Cash flow investing activities	(2,113.4)	(1,641.6)	(1,412.0)
Excluded components recognized within interest expense	$ 35.0	40.0
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flow operating activities		(7.5)	(5.7)
Cash flow investing activities		$ 7.5	$ 5.7
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment related to adoption of new accounting standard					$ (17.1)
Accounting Standards Update 2016-02 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liabilities				$ 380.0
Right-of-use assets				$ 340.0