v3.26.1
Litigation, Claims and Contingencies - Additional Information (Details)
$ in Millions
 9 Months Ended 12 Months Ended
Jun. 30, 2026
USD ($)
ServiceStationProperty
Site
Facility
Jun. 30, 2025
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Sep. 30, 2023
USD ($)
Sep. 30, 2022
USD ($)
Asbestos litigation cost projection [Abstract]            
Number of Years Included in Asbestos Assumption 35 years          
Environmental Remediation Costs Recognized [Abstract]            
Number of sites were company is identified as a potentially responsible party under the superfund or similar state law | Site 52          
Number of current and former operating facilities subject to various environmental laws | Facility 106          
Total number of service station properties subject to various environmental laws | ServiceStationProperty 1,225          
Number of service stations being actively remediated | ServiceStationProperty 15          
Recorded third-party environmental recoveries receivables $ 13   $ 14      
Recorded third-party environmental recoveries, noncurrent 12   12      
Environmental exit costs, reasonably possible additional loss $ 480          
Maximum reserve for remediation reserve related to any one site (in hundredths) 21.00%          
Ashland [Member]            
Asbestos reserve [Roll Forward]            
Increase (decrease) in asbestos related reserve $ 31 $ 16 16 $ 24 $ 9  
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable 103 [1],[2] 96 [1],[2] 95 [1],[2] 97 [1],[2] 95 [1],[2] $ 101
Receivable adjustment 15          
Asbestos litigation cost projection [Abstract]            
Possible total future litigation defense and claim settlement costs 375          
Total reserves for asbestos claims 262 [3] 265 [3] 258 [3] 274 [3] 281 [3] 305
Hercules [Member]            
Asbestos reserve [Roll Forward]            
Increase (decrease) in asbestos related reserve 17 10 10 14 (2)  
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]            
Insurance receivable 53 [4],[5] 49 [4],[5] 48 [4],[5] 50 [4],[5] 47 [4],[5] 52
Receivable adjustment 7          
Asbestos litigation cost projection [Abstract]            
Possible total future litigation defense and claim settlement costs 256          
Total reserves for asbestos claims $ 183 [6] $ 185 [6] $ 177 [6] $ 185 [6] $ 191 [6] $ 213
[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 $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.
[4] 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.
[5] The allowance for credit losses was $1 million at both June 30, 2026 and September 30, 2025.
[6] 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.