Supplemental Information (Other Noncurrent Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Disclosure Text Block Supplement [Abstract]
Operating lease right-of-use assets	$ 376.8
Deferred tax assets	115.1	$ 115.2
Derivative instruments	45.8	81.7
Noncurrent customer receivable	0.0	118.0
Prepaid tax	19.3	17.0
Pension benefits	26.5	28.7
Long-term deposits on plant and equipment	100.0	0.0
Other	259.6	243.5
Other noncurrent assets	$ 943.1	$ 604.1