Litigation, Claims and Contingencies - Summary of Asbestos Claims Activity (Details) - Claim Claim in Thousands	6 Months Ended	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Ashland [Member]
Asbestos claims [Roll Forward]
Open claims - beginning of year	40	41	41	42	44
New claims filed	1	1	2	2	2
Claims settled	0	0	0	(1)	(1)
Claims dismissed	(1)	(1)	(3)	(2)	(3)
Open claims - end of period	40	41	40	41	42
Hercules [Member]
Asbestos claims [Roll Forward]
Open claims - beginning of year	11	12	12	11	12
New claims filed	1	1	1	1	1
Claims dismissed	(1)	(1)	(2)	0	(2)
Open claims - end of period	11	12	11	12	11

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Number of claims dismissed.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

+ Details

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- Definition

Number of claims settled.

+ References

+ Details

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- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

+ Details

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- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

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- Details

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- Details

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