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Restructuring - Additional Information (Details) - USD ($) $ in Millions | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024
Restructuring Cost and Reserve [Line Items] |  |
Cash payment for restructuring | $ 4 | $ 6
RM Plan and PC Plan [Member] |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance costs | 1 | $ 13
Cash payment for restructuring | 1 |
2025 Reorganizations [Member] |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance costs | 10 |
Expected additional restructuring charges | 1 |
Cash payment for restructuring | $ 7 |

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- Definition Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 420 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482017/420-10-50-1 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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