Selected Balance Sheet Information - Inventories (Details) - USD ($) $ in Thousands |
Mar. 31, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Public Utilities, Inventory [Line Items] | ||
| Inventories | $ 380,396 | $ 358,812 |
| Materials and supplies | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 259,968 | 245,857 |
| Coal and fuel oil | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 61,232 | 62,238 |
| Urea | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 20,891 | 18,786 |
| Ammonia | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 14,655 | 9,233 |
| Ammonium sulfate | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 7,952 | 5,081 |
| Lime and limestone | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 7,886 | 8,484 |
| Natural gas held in storage | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | 1,688 | 2,055 |
| Other | ||
| Public Utilities, Inventory [Line Items] | ||
| Inventories | $ 6,124 | $ 7,078 |