Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disclosure Text Block Supplement [Abstract]
Facility closure	$ 0.0	$ 29.0	$ 0.0	$ 0.0
Equity affiliates and joint venture partners
Related Party Transaction [Line Items]
Sales to and other income from related parties		$ 410.0	$ 360.0	$ 600.0

Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Name:	us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration