| Additional Financial Statement Information | 3.Additional Financial Statement Information  Balance Sheet  Other balance sheet information is as follows:  
|  |  |  |  |  |  |  |  
| (in thousands) |      | September 30,  | December 31, |  
|  |      | 2024 | 2023 |  
| Other Receivables |  |  |  |  |  |  |  
| Insurance and Third Party Receivables for Remediation Expenses |  | $ |  5,427 |  | $ |  4,064 |  
| Reimbursable Research and Development Receivable |  |  |  — |  |  |  1,450 |  
| Property Insurance Receivable |  |  |  2,337 |  |  |  4,000 |  
| Financing Receivable |  |  |  4,004 |  |  |  — |  
| Reimbursable Projects  |  |  |  3,524 |  |  |  3,253 |  
| Total Other Receivables |  | $ |  15,292 |  | $ |  12,767 |  
|  |  |  |  |  |  |  |  
| Prepaids and Deposits |  |  |  |  |  |  |  
| Prepaid Insurance  |  | $ |  318 |  | $ |  5,494 |  
| Other Prepaids and Deposits |  |  |  4,141 |  |  |  2,870 |  
| Total Prepaids and Deposits |  | $ |  4,459 |  | $ |  8,364 |  
|  |  |  |  |  |  |  |  
| Accrued and Other Current Liabilities |  |  |  |  |  |  |  
| Accrued Operating Expense |  | $ |  26,157 |  | $ |  33,491 |  
| Accrued Capital Costs |  |  |  3,722 |  |  |  3,812 |  
| Accrued Interest |  |  |  16,147 |  |  |  8,510 |  
| Accrued Compensation |  |  |  10,269 |  |  |  10,118 |  
| Accrued General and Administrative Expense |  |  |  1,787 |  |  |  1,030 |  
| Sales Tax Payable |  |  |  7,667 |  |  |  1,645 |  
| Operating Lease Liabilities |  |  |  1,631 |  |  |  1,676 |  
| Finance Lease Liabilities |  |  |  205 |  |  |  — |  
| Contingent Consideration Liability |  |  |  1,056 |  |  |  1,221 |  
| Advance Billings for Reimbursable Research and Development Expense |  |  |  1,378 |  |  |  1,120 |  
| Other  |  |  |  4,811 |  |  |  1,793 |  
| Total Accrued and Other Current Liabilities |  | $ |  74,830 |  | $ |  64,416 |  
|  |  |  |  |  |  |  |  
| Other Long-Term Liabilities |  |  |  |  |  |  |  
| Noncurrent Operating Lease Liabilities |  | $ |  14,333 |  | $ |  14,716 |  
| Noncurrent Finance Lease Liabilities |  |  |  627 |  |  |  — |  
| Contingent Consideration Liability  |  |  |  1,690 |  |  |  2,078 |  
| Total Other Long-Term Liabilities |  | $ |  16,650 |  | $ |  16,794 |   Statement of Operations  Other statement of operations information is as follows:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| (in thousands) |  | Three Months Ended  |  | Nine Months Ended  |  
|  |  | September 30,  |  | September 30,  |  
|  |      | 2024 |      | 2023 |      | 2024 |      | 2023 |  
| Depreciation, Amortization and Accretion Expense |  |  |  |  |  |  |  |  |  |  |  |  |  
| Depreciation of Property, Plant and Equipment |  | $ |  10,351 |  | $ |  9,749 |  | $ |  30,295 |  | $ |  27,946 |  
| Amortization of Intangible Assets |  |  |  9,263 |  |  |  9,392 |  |  |  27,790 |  |  |  28,295 |  
| Accretion of Asset Retirement Obligations |  |  |  351 |  |  |  304 |  |  |  1,008 |  |  |  896 |  
| Amortization of Finance Right-of-Use Assets |  |  |  9 |  |  |  — |  |  |  9 |  |  |  — |  
| Total Depreciation, Amortization and Accretion Expense |  | $ |  19,974 |  | $ |  19,445 |  | $ |  59,102 |  | $ |  57,137 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Other Operating (Income) Expense, Net |  |  |  |  |  |  |  |  |  |  |  |  |  
| (Gain) Loss on Disposal of Assets, Net |  | $ |  (30) |  | $ |  (2,631) |  | $ |  84 |  | $ |  (2,574) |  
| Abandoned Projects  |  |  |  78 |  |  |  — |  |  |  823 |  |  |  128 |  
| Transaction Costs |  |  |  (36) |  |  |  528 |  |  |  60 |  |  |  673 |  
| Other |  |  |  (370) |  |  |  (18) |  |  |  (588) |  |  |  (323) |  
| Other Operating (Income) Expense, Net |  | $ |  (358) |  | $ |  (2,121) |  | $ |  379 |  | $ |  (2,096) |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Interest Expense |  |  |  |  |  |  |  |  |  |  |  |  |  
| Interest on Debt Instruments |  | $ |  8,678 |  | $ |  8,373 |  | $ |  25,575 |  | $ |  25,477 |  
| Amortization of Debt Issuance Costs |  |  |  764 |  |  |  612 |  |  |  2,293 |  |  |  1,830 |  
| Interest on Finance Lease Obligations |  |  |  2 |  |  |  — |  |  |  2 |  |  |  — |  
| Total Interest Expense |  |  |  9,444 |  |  |  8,985 |  |  |  27,870 |  |  |  27,307 |  
| Less: Capitalized Interest |  |  |  (62) |  |  |  (1,030) |  |  |  (1,237) |  |  |  (3,720) |  
| Total Interest Expense, Net |  | $ |  9,382 |  | $ |  7,955 |  | $ |  26,633 |  | $ |  23,587 |   |