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Litigation, Claims and Contingencies - Summary of Asbestos Claims Activity (Details) - Claim Claim in Thousands | 6 Months Ended | 12 Months Ended
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Mar. 31, 2025 | Mar. 31, 2024 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
Ashland [Member] |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |
Open claims - beginning of year | 41 | 42 | 42 | 44 | 46
New claims filed | 1 | 1 | 2 | 2 | 2
Claims settled | 0 | 0 | (1) | (1) | (1)
Claims dismissed | (1) | (1) | (2) | (3) | (3)
Open claims - end of period | 41 | 42 | 41 | 42 | 44
Hercules [Member] |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |
Open claims - beginning of year | 12 | 12 | 12 | 11 | 12
New claims filed | 1 | 1 | 1 | 1 | 1
Claims dismissed | (1) | (1) | (1) | 0 | (2)
Open claims - end of period | 12 | 12 | 12 | 12 | 11

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