Derivative Financial Instruments Interest Rate Swaps (Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position) (Details) - Interest Rate Swap [Member] - Designated as Hedging Instrument [Member] - Other Noncurrent Liabilities [Member] - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 755.8	$ 711.0
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 5.8	$ (39.0)