ACQUISITIONS, Acquisition and Disposition-Related Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Total Acquisition-related expenses	$ 19	$ 0	$ 0
Disposition-related expenses	0	7	15
Total Acquisition and disposition-related expenses	19	7	15
Capital Markets
Business Acquisition [Line Items]
Disposition-related expenses		7	15
Legal
Business Acquisition [Line Items]
Total Acquisition-related expenses	7	0	0
Identifiable intangible amortization
Business Acquisition [Line Items]
Total Acquisition-related expenses	6	0	0
Other professional fees
Business Acquisition [Line Items]
Total Acquisition-related expenses	$ 6	$ 0	$ 0