v3.26.1
Litigation, Claims and Contingencies - Summary of Progression of Insurance Receivable (Parenthetical) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Sep. 30, 2025
Jun. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Ashland [Member]            
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable $ 103 [1],[2] $ 95 [1],[2] $ 96 [1],[2] $ 97 [1],[2] $ 95 [1],[2] $ 101
Allowance for credit losses 1 1        
Ashland [Member] | Accounts Receivable [Member]            
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable 10 10        
Hercules [Member]            
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable 53 [3],[4] 48 [3],[4] $ 49 [3],[4] $ 50 [3],[4] $ 47 [3],[4] $ 52
Allowance for credit losses 1 1        
Hercules [Member] | Accounts Receivable [Member]            
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable $ 7 $ 6        
[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.