Revenue - Additional Information (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Sep. 30, 2025 |
|
| Product Concentration Risk [Member] | Sales Revenue [Member] | Minimum [Member] | |||||
| Revenue From Contracts With Customers [Line Items] | |||||
| Concentration risk percentage | 10.00% | ||||
| Cellulosics [Member] | Product Concentration Risk [Member] | Sales Revenue [Member] | |||||
| Revenue From Contracts With Customers [Line Items] | |||||
| Concentration risk percentage | 40.00% | 40.00% | 40.00% | 39.00% | |
| Polyvinylpyrrolidones (PVP) [Member] | Product Concentration Risk [Member] | Sales Revenue [Member] | |||||
| Revenue From Contracts With Customers [Line Items] | |||||
| Concentration risk percentage | 24.00% | 25.00% | 24.00% | 25.00% | |
| Trade Receivable [Member] | |||||
| Revenue From Contracts With Customers [Line Items] | |||||
| Trade receivables | $ 203 | $ 203 | $ 200 | ||