v3.26.1
Litigation, Claims and Contingencies - Schedule of Progression of Activity in the Asbestos Litigation Reserves (Details) - USD ($)
$ in Millions
 9 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Ashland [Member]          
Asbestos reserve [Roll Forward]          
Asbestos litigation reserves - beginning of year $ 258 [1] $ 274 [1] $ 274 [1] $ 281 [1] $ 305
Reserve adjustment 31 16 16 24 9
Amounts paid (27) (25) (32) (31) (33)
Asbestos litigation reserves - end of period [1] 262 265 258 274 281
Hercules [Member]          
Asbestos reserve [Roll Forward]          
Asbestos litigation reserves - beginning of year 177 [2] 185 [2] 185 [2] 191 [2] 213
Reserve adjustment 17 10 10 14 (2)
Amounts paid (11) (10) (18) (20) (20)
Asbestos litigation reserves - end of period [2] $ 183 $ 185 $ 177 $ 185 $ 191
[1] Includes $29 million classified in accrued expenses and other liabilities within the Condensed Consolidated Balance Sheets as of both June 30, 2026 and September 30, 2025.
[2] Includes $17 million classified in accrued expenses and other liabilities within the Condensed Consolidated Balance Sheets at both June 30, 2026 and September 30, 2025.