Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Dec. 31, 2018	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Disclosure Text Block Supplement [Abstract]
Trade receivables, net			$ 90.0	$ 95.0
Facility closure	$ 23.2	$ 29.0	23.2	0.0	$ 29.0
Facility closure	(23.2)	$ (29.0)	(23.2)	0.0	(29.0)
Net proceeds from sale of property	$ 44.1
Company headquarters relocation income (expense)			0.0	33.8	0.0
Cost reduction actions			0.0	0.0	25.5
Equity affiliates and joint venture partners
Related Party Transaction [Line Items]
Sales to and other income from related parties			$ 225.0	$ 335.0	$ 410.0