Summary of Significant Accounting Policies - Capitalized Direct Costs (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment, Gross [Abstract]
Capitalized computer software, gross	$ 22.7	$ 18.2
Capitalized computer software costs	4.4
Software Development
Property, Plant and Equipment, Gross [Abstract]
Capitalized computer software, gross	$ 5.8

Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Name:	us-gaap_CapitalizedComputerSoftwareGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant