Restructuring - Summary of Details of Plant Closures and Restructuring Liabilities (Details) - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended |
|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
|
| Workforce reduction program | ||
| Restructuring Reserve [Roll Forward] | ||
| Balance at beginning of period | $ 0.6 | $ 4.4 |
| Accrual | 0.0 | 1.2 |
| Cash paid | (0.6) | (5.0) |
| Balance at end of period | 0.0 | 0.6 |
| Stickney Shutdown | ||
| Restructuring Reserve [Roll Forward] | ||
| Balance at beginning of period | 0.0 | 0.0 |
| Accrual | 38.4 | 0.0 |
| Cash paid | (0.0) | (0.0) |
| Balance at end of period | 38.4 | 0.0 |
| Short-term, asset retirement obligation | 18.5 | |
| Phthalic Anhydride Shutdown | ||
| Restructuring Reserve [Roll Forward] | ||
| Balance at beginning of period | 5.4 | 0.0 |
| Accrual | 1.3 | 13.5 |
| Cash paid | (2.3) | (8.1) |
| Balance at end of period | $ 4.4 | $ 5.4 |