v3.26.1
Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (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]          
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]          
Insurance receivable - beginning of year $ 95 [1],[2] $ 97 [1],[2] $ 97 [1],[2] $ 95 [1],[2] $ 101
Receivable adjustment 15 5 5 11 3
Amounts collected (7) (6) (7) (9) (9)
Insurance receivable - end of period [1],[2] 103 96 95 97 95
Hercules [Member]          
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]          
Insurance receivable - beginning of year 48 [3],[4] 50 [3],[4] 50 [3],[4] 47 [3],[4] 52
Receivable adjustment 7 4 4 6 (3)
Amounts collected (2) (5) (6) (3) (2)
Insurance receivable - end of period [3],[4] $ 53 $ 49 $ 48 $ 50 $ 47
[1] Includes $10 million classified in accounts receivable, net within the Condensed Consolidated Balance Sheets at both June 30, 2026 and September 30, 2025.
[2] The allowance for credit losses was $1 million at both June 30, 2026 and September 30, 2025.
[3] Includes $7 million and $6 million classified in accounts receivable, net on the Condensed Consolidated Balance Sheets at June 30, 2026 and September 30, 2025, respectively.
[4] The allowance for credit losses was $1 million at both June 30, 2026 and September 30, 2025.