Debt (Summary of Outstanding Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Debt Disclosure [Abstract]
Short-term borrowings	$ 2.4	$ 7.7
Current portion of long-term debt	484.5	470.0
Long-term debt	6,875.7	7,132.9
Long-term debt – related party	274.6	297.2
Total Debt	$ 7,637.2	$ 7,907.8
Short-term debt, weighted average interest rate	0.60%	1.60%
Current portion of long-term debt due to related party	$ 83.8	$ 41.3