Accounts Receivable Facility (Narrative) (Details) - Accounts receivable sales agreement - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020
Transfer of Financial Assets Accounted for as Sales [Line Items]
Accounts receivable sold through AR Facility	$ 293.9	$ 245.3	$ 634.2	$ 646.5
Transfer of accounts receivable, sales amount derecognized	136.1		136.1		$ 77.0
Loss on sale of accounts receivable	$ 0.2	$ 0.2	$ 0.6	$ 1.1

Amount of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction, at the date of derecognition.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=SL51823488-111719

Name:	us-gaap_TransferOfFinancialAssetsAccountedForAsSalesAmountDerecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant