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Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Disclosure Text Block Supplement [Abstract]
Net proceeds from sale of property			$ 44.1
Company headquarters relocation income (expense)	$ 0.0	$ 0.0	$ 33.8	$ 0.0		$ 33.8	$ 0.0	$ 0.0
Facility closure					$ 29.0	0.0	29.0	0.0
Related Party Transaction [Line Items]
Trade receivables, net	$ 95.0					95.0	130.0
Equity affiliates and joint venture partners
Related Party Transaction [Line Items]
Sales to and other income from related parties						$ 335.0	$ 410.0	$ 360.0