Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Tax benefit related to TCJA	$ 0	$ 9,847	$ 0

Amount of reasonable estimate for income tax benefit for which accounting for tax effect for remeasurement of deferred tax liability from change in tax rate is incomplete pursuant to Tax Cuts and Jobs Act.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2A
-Subparagraph (SAB Topic 5.EE.Q2(b))
-URI http://asc.fasb.org/extlink&oid=116825942&loc=SL116722634-122817

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