SEGMENT INFORMATION - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Goodwill impairment	$ 0	$ 19	$ 0
Capital Markets
Segment Reporting Information [Line Items]
Goodwill impairment		$ 19

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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