Fair Value - Summary of Activity Under A/R Sales Agreement (Details) - USD ($) $ in Millions	9 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Receivable from financial institution at beginning of fiscal year		$ 24.9
Receivables sold to the financial institution and derecognized	$ 1,453.5	1,194.2
Receivables collected by financial institution	(1,441.6)	(1,183.2)
Cash paid to (proceeds from) financial institution	$ (11.9)	(24.0)
Receivable from financial institution at June 30		$ 11.9

Cash Flows between a transferor and a transferee attributable to collections reinvested in revolving period transfers related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

Name:	us-gaap_CashFlowsBetweenTransfereeAndTransferorProceedsFromCollectionsReinvestedInRevolvingPeriodTransfers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration