NATURE OF BUSINESS, SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND OTHER - Accrued Liabilities (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($)
Accrued liabilities current [abstract]
Accrued employee-related costs	$ 116	$ 109
Accrued taxes other than on income	57	38
Asset retirement obligation	28	31
Accrued interest	13	15
Lease liability	28
Other	71	24
Accrued liabilities	$ 313	$ 217
Organizational Changes
Accrued liabilities current [abstract]
Number of positions remaining | employee	1,250
Incurred cost	$ 41
Expected cost remaining	19
Employee Salary and Severance
Accrued liabilities current [abstract]
Incurred cost	29
Other Termination Benefits
Accrued liabilities current [abstract]
Incurred cost	$ 12