Discontinued Operations, Goodwill, and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Estimated amortization expense for the succeeding years
2021 (nine months remaining)	$ 15,400
2022	19,700
2023	18,800
2024	17,400
2025	700
Intangible Assets, Net	72,003		$ 76,917
Amortization expense	$ 5,400	$ 6,100

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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