Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Intangible assets subject to amortization, beginning balance			$ 15,363
Intangible assets subject to amortization, Amortization	$ (400)	$ (400)	(1,275)	$ (1,300)
Intangible assets subject to amortization, ending balance	$ 14,088		$ 14,088

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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