| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| OPERATING ACTIVITIES: | | | | | | | | |
| Net income (loss) | 18.1 | -3.8 | | | | | | |
| Deferred income taxes | 1.8 | 0.0 | -2.1 | -21.8 | -2.3 | -16.4 | -3.9 | 7.5 |
| Equity income (loss) – Sunrise Energy | -0.4 | -0.4 | -1.1 | 0.5 | 0.2 | -0.4 | 1.4 | 1.6 |
| Cash distribution - Sunrise Energy | | | 1.1 | | | 0.2 | 4.0 | |
| Depreciation, depletion and amortization | 46.9 | 40.0 | 39.6 | 48.6 | 44.2 | 38.5 | 35.6 | 43.9 |
| Loss on sale of assets | -0.3 | 0.3 | 0.0 | -0.1 | 0.6 | | | |
| Change in fair value of interest rate swaps | | | | | | | | |
| Amortization of debt issuance costs | 3.6 | 2.6 | 2.3 | 2.1 | 2.0 | 1.8 | 2.3 | 1.4 |
| Asset retirement obligations accretion | 1.0 | 1.5 | 1.4 | 1.3 | 1.2 | 0.9 | 1.0 | 0.5 |
| Cash paid on asset retirement obligation reclamation | -3.2 | | | | | | | |
| Stock-based compensation | 1.3 | 1.0 | 1.2 | 1.8 | 3.2 | 7.3 | 2.5 | 3.1 |
| Provision for loss on customer contracts | 0.2 | | | | | | | |
| Amortization of contract asset and contract liabilities | -19.7 | | | | | | | |
| Other | 0.7 | -0.4 | -3.0 | 2.6 | 0.4 | -1.4 | -3.1 | -0.9 |
| Change in operating assets and liabilities: | | | | | | | | |
| Accounts receivable | -16.3 | 0.8 | 11.2 | -7.3 | -1.7 | 5.5 | -5.6 | 10.6 |
| Inventory | -25.9 | 17.0 | 2.9 | -8.6 | -7.7 | -2.7 | 4.8 | 4.8 |
| Parts and supplies | -6.3 | -1.1 | 2.9 | -2.1 | -0.4 | | | |
| Prepaid expenses | -5.9 | -5.2 | | | -4.9 | -4.8 | -2.6 | 0.4 |
| Accounts payable and accrued liabilities | 24.0 | 10.8 | -1.4 | 3.6 | 5.7 | -0.8 | -11.2 | -1.7 |
| Deferred revenue | 35.5 | | | | | | | |
| Cash provided by operating activities | 54.2 | 48.0 | 52.6 | 38.2 | 51.6 | 65.8 | 60.9 | 94.7 |
| |
| INVESTING ACTIVITIES: | | | | | | | | |
| Capital expenditures | -54.0 | -28.1 | -20.7 | -35.5 | | | | |
| Proceeds from sale of equipment | 0.7 | 0.5 | 0.1 | 0.1 | 0.1 | 0.5 | | |
| Cash used in investing activities | -53.4 | -27.5 | -18.2 | -30.2 | -26.0 | -22.3 | -49.3 | -30.5 |
| |
| FINANCING ACTIVITIES: | | | | | | | | |
| Payments on bank debt | -78.2 | -46.2 | -49.7 | -42.1 | -38.8 | -36.6 | -34.9 | -56.9 |
| Borrowings of bank debt | 51.7 | 20.3 | 2.8 | 33.8 | | | | |
| Issuance of convertible note | 11.0 | | | | | | | |
| Debt issuance costs | -2.1 | -0.4 | -1.9 | -1.2 | -0.7 | | -2.1 | |
| Taxes paid on vesting of RSUs | | -0.3 | -0.1 | -0.4 | -0.3 | -3.2 | | |
| Cash (used in) provided by financing activities | -0.2 | -26.7 | -35.6 | -14.8 | -21.8 | -39.8 | -17.7 | -61.7 |
| |
| CASH, CASH EQUIVALENTS, AND RESTRICTED CASH CONSIST OF THE FOLLOWING: | | | | | | | | |
| Cash and cash equivalents | | | | | | | | |
| Restricted cash | | | | | | | | |
| SUPPLEMENTAL CASH FLOW INFORMATION: | | | | | | | | |
| Cash paid for interest | 8.1 | 8.7 | 11.0 | 11.6 | 11.4 | 11.7 | 12.4 | 14.1 |
| SUPPLEMENTAL NON-CASH FLOW INFORMATION: | | | | | | | | |
| Change in capital expenditures included in accounts payable and prepaid expense | 3.4 | 8.5 | 1.2 | 5.8 | | 7.6 | | 0.8 |