Discontinued Operations, Goodwill, and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020
Estimated amortization expense for the succeeding years
2021 (six months remaining)	$ 4,900
2022	19,800
2023	18,800
2024	17,400
2025	800
Intangible Assets, Net	61,666		$ 76,917
Amortization expense	$ 15,900	$ 18,300

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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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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