Derivative Instruments - Summary of Company's Outstanding Interest Rate Swap Contracts (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Interest rate swap contracts
Derivative [Line Items]
Interest rate swap and foreign currency contracts	$ 1,220,000	$ 1,220,000

Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant