SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Recent Accounting Developments (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Oct. 01, 2019
Lessee, Lease, Description [Line Items]
Accounting standards update	us-gaap:AccountingStandardsUpdate201602Member	us-gaap:AccountingStandardsUpdate201601Member
Lease ROU assets	$ 321	$ 0
Present value of lease liabilities	$ 345
Operating lease, right of use asset, statement of financial position, extensible list	us-gaap:OtherAssets
Operating lease, liability, statement of financial position, extensible list	us-gaap:OtherLiabilities
Other assets
Lessee, Lease, Description [Line Items]
Lease ROU assets			$ 333
Other payables
Lessee, Lease, Description [Line Items]
Present value of lease liabilities			$ 357