INCOME TAXES, Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax penalties and interest accrued	$ 8	$ 6
Changes in the liability for unrecognized tax benefits [Roll Forward]
Uncertain tax positions beginning of year	42	31	$ 20
Increases for tax positions related to the current year	5	11	5
Increases for tax positions related to prior years	3	7	10
Decreases for tax positions related to prior years	(1)	0	(1)
Decreases due to lapsed statute of limitations	(4)	(2)	(3)
Decreases related to settlements	0	(5)	0
Uncertain tax positions end of year	45	42	31
Unrecognized tax benefits that would impact effective tax rate	40	$ 38	$ 27
Decrease in unrecognized tax benefits is reasonably possible	$ 8