GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details) - USD ($)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Amortization expense	$ 85,557,000	$ 59,931,000	$ 7,495,000
Goodwill impairment loss	0	0	$ 0
Goodwill	1,205,000
Carrying value of intangible assets	$ 47,170,000	$ 47,170,000
Pipeline
Goodwill [Line Items]
Fair value in excess of carrying value, percent	8.00%
Goodwill impairment loss	$ 0
Goodwill	318,200,000
Carrying value of intangible assets	$ 46,000,000.0

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 of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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Percentage of fair value of reporting unit in excess of carrying amount.

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