INCOME TAXES (Unrecognized tax benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2015
Total amount of unrecognized tax benefits that, if recognized, would affect the tax rate for continuing and discontinued operations	$ 171
Interest and penalties related to uncertain tax positions	3		$ 5	$ (1)
Interest and penalties related to unrecognized tax benefits accrued	26		21
Tax indemnity receivable	86		82
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	168		144
Increases related to positions taken on items from prior years	8		10
Decreases related to positions taken on items from prior years	(3)		(4)
Increases related to positions taken in the current year	14		22
Lapse of statute of limitations	3		(2)
Acquisition of Pharmachem	11
Settlement of uncertain tax positions with tax authorities	(1)		(2)
Balance at end of period	194	[1]	$ 168	$ 144
Maximum [Member]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	22
Minimum [Member]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	32
Valvoline [Member]
Tax indemnity receivable	$ 48

[1] Ashland has offsetting indemnity receivables from Valvoline and Pharmachem for $48 million of the gross unrecognized tax benefits balance at September 30, 2017.