Derivative Financial Instruments - Additional Information (Details) - CAD ($)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Canadian Dollar Forward Contract
Derivative [Line Items]
Foreign currency forward contract to hedge	$ 0	$ 7,000,000.0
Canadian Subsidiary
Derivative [Line Items]
Denominated intercompany accounts payable	$ 3,400,000	$ 9,300,000

Amount for accounts payable to related parties.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant