v3.25.2
Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Reserve (Parenthetical) (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Sep. 30, 2024
Jun. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Ashland [Member]            
Asbestos reserve [Roll Forward]            
Asbestos reserve $ 265 [1] $ 274 [1] $ 282 [1] $ 281 [1] $ 305 [1] $ 320
Ashland [Member] | Other Current Liabilities [Member]            
Asbestos reserve [Roll Forward]            
Asbestos reserve 29 28        
Hercules [Member]            
Asbestos reserve [Roll Forward]            
Asbestos reserve 185 [2] 185 [2] $ 190 [2] $ 191 [2] $ 213 [2] $ 217
Hercules [Member] | Other Current Liabilities [Member]            
Asbestos reserve [Roll Forward]            
Asbestos reserve $ 17 $ 17        
[1] Includes $29 million and $28 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets as of June 30, 2025 and September 30, 2024, respectively.
[2] Includes $17 million classified in accrued expenses and other liabilities on the Condensed Consolidated Balance Sheets at both June 30, 2025 and September 30, 2024.