Stock repurchase program amount outstanding.

No definition available.

Name:	ash_StockRepurchaseProgramAmountOutstanding
Namespace Prefix:	ash_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147481520/505-30-50-4

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

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Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount remaining authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

+ References

No definition available.

+ Details

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

- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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+ Details

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Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

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Equity Items - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024	Jun. 28, 2023
Accelerated Share Repurchases [Line Items]
Stock repurchase during period value	$ 100		$ 0		$ 100	$ 100
Accrued expenses and other liabilities	$ 209				209		$ 256
Dividend per common share	$ 40.5	$ 40.5	$ 38.5	$ 38.5
2022 Stock Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchase program amount outstanding								$ 200
2023 Stock Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Aggregate amount of common stock to be repurchased								$ 1,000
Stock Repurchase Program, Remaining Repurchase Amount	$ 520				$ 520