Restructuring - Summary of Restructuring Expense and Gains (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 14,025	$ (682)	$ 33,615
Total expense (gain)	14,025	(682)	33,615
Project Surge
Restructuring Cost And Reserve [Line Items]
Restructuring expense	1,511
Restructuring charges	1,511
Transformation Plan
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 12,514	$ (682)	$ 33,615

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

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