Summary of Significant Accounting Policies - Income Taxes (Details)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accounting Policies [Abstract]
Effective income tax rate reconciliation, at federal statutory income tax rate, percent (as a percentage)	21.00%	21.00%	24.50%

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration