STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (LOSS) (unaudited) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Sales		$ 974	$ 806	$ 1,816	$ 1,510
Cost of sales		699	578	1,312	1,093
Gross profit		275	228	504	417
Selling, general and administrative expense		163	155	334	312
Research and development expense		21	21	43	41
Equity and other income		4	1	6	4
Operating income		95	53	133	68
Net interest and other financing expense		29	29	59	152
Other net periodic benefit income		1	0	1	3
Net loss on divestitures		0	0	1	1
Income (loss) from continuing operations before income taxes		67	24	74	(82)
Income tax expense (benefit)		1	(5)	15	(45)
Income (loss) from continuing operations		66	29	59	(37)
Income from discontinued operations (net of income taxes)		7	76	10	152
Net income		73	105	69	115
Net income attributable to noncontrolling interest	[1]	0	13	0	24
Net income attributable to Ashland		$ 73	$ 92	$ 69	$ 91
Basic earnings per share - Note L
Income (loss) from continuing operations		$ 1.06	$ 0.46	$ 0.94	$ (0.59)
Income from discontinued operations attributable to Ashland		0.11	1.02	0.16	2.06
Net income attributable to Ashland		1.17	1.48	1.10	1.47
Diluted earnings per share - Note L
Income (loss) from continuing operations		1.04	0.46	0.93	(0.59)
Income from discontinued operations attributable to Ashland		0.11	1.01	0.15	2.06
Net income attributable to Ashland		$ 1.15	$ 1.47	$ 1.08	$ 1.47
COMPREHENSIVE INCOME (LOSS)
Net income		$ 73	$ 105	$ 69	$ 115
Other comprehensive income (loss), net of tax
Unrealized translation gain (loss)		55	60	58	(86)
Pension and postretirement obligation adjustment		0	(2)	0	(4)
Net change in available-for-sale securities		(6)	6	2	6
Other comprehensive income (loss)		49	64	60	(84)
Comprehensive income		122	169	129	31
Comprehensive income attributable to noncontrolling interest		0	14	0	24
Comprehensive income attributable to Ashland		$ 122	$ 155	$ 129	$ 7

[1] For the three and six months ended March 31, 2017, this represents the income attributable to the previous noncontrolling interest in Valvoline Inc., whose results are now included within discontinued operations. See Note B for more information.