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Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Reserve (Parenthetical) (Details) - USD ($) $ in Millions | Jun. 30, 2020 | Sep. 30, 2019 | Jun. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
--- | --- | --- | --- | --- | --- | ---
Ashland [Member] |  |  |  |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |  |  |  |
Asbestos reserve | $ 341 | [1] | $ 352 | [1] | $ 360 | $ 380 | $ 419 | $ 415
Ashland [Member] | Other Current Liabilities [Member] |  |  |  |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |  |  |  |
Asbestos reserve | 29 |  | 28 |  |  |  |  |
Hercules [Member] |  |  |  |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |  |  |  |
Asbestos reserve | 235 | [2] | 252 | [2] | $ 257 | $ 282 | $ 323 | $ 321
Hercules [Member] | Other Current Liabilities [Member] |  |  |  |  |  |  |  |
Asbestos claims [Roll Forward] |  |  |  |  |  |  |  |
Asbestos reserve | $ 22 |  | $ 21 |  |  |  |  |
[1] | Included $29 million and $28 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of both June 30, 2020 and September 30, 2019.
[2] | Included $22 million and $21 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of both June 30, 2020 and September 30, 2019.

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- Definition Amount of valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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