LEASES - Operating Lease Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease assets	$ 321	$ 0
Operating lease liabilities	$ 345
Weighted-average remaining lease term (years)	5 years
Weighted-average discount rate	3.86%
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