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.

No definition available.

+ Details

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

- Definition

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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

- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.P.3)
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140864-122747

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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

- Details

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Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_FacilityClosingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=ash_VoluntarySeveranceOfferMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
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Balance Type:
Period Type:

- Details

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- Details

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Data Type:	na
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Restructuring Activities - Additional Information (Details) - USD ($)	3 Months Ended			9 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	$ 22,000,000	$ 43,000,000		$ 22,000,000
Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs			$ 0		$ 0
Restructuring reserve	14,000,000	36,000,000		14,000,000
Facility Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0		$ 8,000,000	8,000,000	$ 8,000,000
Restructuring reserve	8,000,000	7,000,000		8,000,000
Voluntary Severance Offer [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs		$ 36,000,000
Voluntary Severance Offer [Member] \| Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs	3,000,000			7,000,000
Plant Restructuring [Member] \| Severance Costs [Member] \| Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs				5,000,000
Restructuring reserve	1,000,000			1,000,000
Plant Restructuring [Member] \| Accelerated Depreciation and Amortization [Member] \| Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs				38,000,000
Plant Restructuring [Member] \| Plant Closure Costs [Member] \| Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs				4,000,000
Restructuring reserve	2,000,000			2,000,000
Plant Restructuring [Member] \| Cost of Sales [Member] \| Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 0			$ 47,000,000