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v3.25.1

Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Reserve (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Mar. 31, 2024 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
Ashland [Member] |  |  |  |  |  |  |  |  |  |
Asbestos reserve [Roll Forward] |  |  |  |  |  |  |  |  |  |
Asbestos reserve - beginning of year |  | $ 274 | [1] | $ 281 | [1] | $ 281 | [1] | $ 305 | [1] | $ 320
Reserve adjustment |  | 0 |  | 0 |  | 24 |  | 9 |  | 16
Amounts paid |  | (18) |  | (18) |  | (31) |  | (33) |  | (31)
Asbestos reserve - end of period | [1] | 256 |  | 263 |  | 274 |  | 281 |  | 305
Hercules [Member] |  |  |  |  |  |  |  |  |  |
Asbestos reserve [Roll Forward] |  |  |  |  |  |  |  |  |  |
Asbestos reserve - beginning of year |  | 185 | [2] | 191 | [2] | 191 | [2] | 213 | [2] | 217
Reserve adjustment |  | 0 |  | 0 |  | 14 |  | (2) |  | 15
Amounts paid |  | (5) |  | (11) |  | (20) |  | (20) |  | (19)
Asbestos reserve - end of period | [2] | $ 180 |  | $ 180 |  | $ 185 |  | $ 191 |  | $ 213
[1] | Includes $28 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of March 31, 2025 and September 30, 2024.
[2] | Includes $17 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets at March 31, 2025 and September 30, 2024.

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- Definition Amount of cash outflow to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 17 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-17 + Details
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- Definition Amount of increase (decrease) in valuation and qualifying accounts and reserves from adjustment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4 + Details
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