Sale of interest in subsidiary, shares.

No definition available.

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Namespace Prefix:	ash_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of costs recognized in relation to the separation of the company.

+ References

No definition available.

+ Details

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Namespace Prefix:	ash_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of net assets (liabilities).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 30
-Section 50
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-Name Accounting Standards Codification
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-Topic 946
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-Section S99
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-Subparagraph (SX 210.6-09(7))
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(6))
-URI http://asc.fasb.org/extlink&oid=116637345&loc=SL114874367-224272

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ash_ValvolineIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=ash_ValvolineIncMember
Namespace Prefix:
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Valvoline - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	8 Months Ended	12 Months Ended
	May 12, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Distribution of Valvoline [Line Items]
Distribution of shares	170
Sale of Stock, Percentage of Ownership after Transaction	83.00%
Dividends Payable, fate of record		May 05, 2017
Stockholders' Equity Note, Stock Split, Conversion Ratio	2.745338
Net assets deficit		$ 3,571	$ 3,406
Discontinued Operations [Member]
Distribution of Valvoline [Line Items]
Separation costs				$ 13
Selling, General and Administrative Expense [Member]
Distribution of Valvoline [Line Items]
Separation costs			$ 10	$ 95
Valvoline Inc. [Member]
Distribution of Valvoline [Line Items]
Net assets deficit	$ (187)
Valvoline Inc. [Member]
Distribution of Valvoline [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	17.00%