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.

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Goodwill and Other Intangible Assets - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets		$ 21,812	$ 18,492	$ 17,262
Asset Impairment Charges	$ 0	0
Estimated intangible asset amortization for 2021	21,000	21,000
Estimated intangible asset amortization for 2022	21,000	21,000
Estimated intangible asset amortization for 2023	21,000	21,000
Estimated intangible asset amortization for 2024	21,000	21,000
Estimated intangible asset amortization for 2025	$ 21,000	$ 21,000
Customer Relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Expected remaining useful life		20 years
Customer Relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Expected remaining useful life		15 years
Patents
Finite-Lived Intangible Assets [Line Items]
Expected remaining useful life		17 years
Capitalized software \| Maximum
Finite-Lived Intangible Assets [Line Items]
Expected remaining useful life		7 years
Capitalized software \| Minimum
Finite-Lived Intangible Assets [Line Items]
Expected remaining useful life		3 years