Consolidated interest coverage ratio.

No definition available.

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Namespace Prefix:	ash_
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Period Type:	instant

- Definition

Consolidated leverage ratio.

+ References

No definition available.

+ Details

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

States whether the entity was in compliance with the debt covenants throughout the reporting period, and describes facts and circumstances of any compliance failure.

+ References

No definition available.

+ Details

Name:	ash_CovenantRestrictionsAbstract
Namespace Prefix:	ash_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument maturity year.

+ References

No definition available.

+ Details

Name:	ash_DebtInstrumentMaturityYear
Namespace Prefix:	ash_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

debt instrument Premiums paid.p

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents debt issuance costs that did not qualify for capitalization and was therefore immediately expensed.

+ References

No definition available.

+ Details

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

- Definition

The maximum consolidated leverage ratio permitted under the debt instruments.

+ References

No definition available.

+ Details

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Data Type:	xbrli:decimalItemType
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Period Type:	instant

- Definition

The minimum required consolidated interest coverage ratio under the debt instruments.

+ References

No definition available.

+ Details

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Accelerated amortization of previously capitalized debt issuance costs due to termination or repayment of debt.

+ References

No definition available.

+ Details

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

- Definition

Amount of short-term and long-term debt and lease obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
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+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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

- 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

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of gain (loss) from the difference between the repurchase price of a debt instrument initially issued by the entity and the net carrying amount of the debt at the time of its repurchase.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
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+ Details

Name:	us-gaap_LineOfCredit
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=ash_TwoThousandTwentyCreditAgreementMember
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Balance Type:
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- Details

Name:	us-gaap_DebtInstrumentAxis=ash_A2017RevolvingCreditFacilityMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ash_TwoPointZeroZeroPercentageSeniorNotesDue2028Member
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Balance Type:
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- Details

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Debt - Financing Activity and Covenants - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Jan. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)	Jan. 31, 2020 EUR (€)
Debt Instrument [Line Items]
Payments of debt issuance costs			$ 11
Premiums paid		$ 59	59
Line of credit facility, remaining borrowing capacity		$ 339	$ 339
Covenant restrictions [Abstract]
Maximum consolidated leverage ratio		4.0	4.0	4.0
Consolidated net leverage ratio		3.1	3.1	3.1
Minimum required consolidated interest coverage ratio		3.0	3.0	3.0
Consolidated interest coverage ratio		7.7	7.7	7.7
2020 Credit Agreement [Member]
Debt Instrument [Line Items]
Payments of debt issuance costs			$ 4
Debt issuance costs immediately recognized		$ 1	1
Line of credit facility, maximum borrowing capacity		600	600
2017 Credit Agreement [Member]
Debt Instrument [Line Items]
Repayment of debt, accelerated amortization		$ 1	1
2.00% Senior Notes Due 2028 [Member]
Debt Instrument [Line Items]
Payments of debt issuance costs			$ 8
Debt instrument, interest rate, stated percentage	2.00%	2.00%	2.00%	2.00%	2.00%
Aggregate principal amount \| €				€ 500,000,000	€ 500,000,000
Debt instrument, maturity year			2028
4.750% Notes due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		4.75%	4.75%	4.75%
Debt instrument, maturity year			2022
Repayments of debt			$ 670
Gain (loss) on repurchase of debt instrument		$ (5)	$ (5)
6.875% Notes due 2043 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		6.875%	6.875%	6.875%
Debt instrument, maturity year			2043
Repayments of debt			$ 92
Gain (loss) on repurchase of debt instrument		$ (1)	$ (1)
6.50% Junior Subordinated Notes, Due 2029 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		6.50%	6.50%	6.50%
Debt instrument, maturity year			2029
Repayments of debt		$ 2	$ 2
Accounts Receivable Securitization [Member]
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity		1	1
Unsecured Revolving Credit Facility \| 2020 Credit Agreement [Member]
Debt Instrument [Line Items]
Unsecured line of credit	$ 600
Debt instrument, term	5 years
Unsecured Term Loan Facility [Member] \| 2020 Credit Agreement [Member]
Debt Instrument [Line Items]
Unsecured line of credit	$ 250
Debt instrument, term	5 years
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity		338	338
Debt instrument, outstanding principal amount		240	240
Letters of credit outstanding, amount		$ 22	$ 22