| 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 |
| Revenues: |
| Utility | 860.1 | 663.7 | 652.1 | 735.4 | | | | |
| Other | 1.3 | 3.9 | | | | | | |
| Total revenues | 861.4 | 667.6 | 645.0 | 720.6 | 743.8 | 639.0 | 728.6 | 1,411.5 |
| Revenue growth [+] | 29.0% | 3.5% | -10.5% | -3.1% | 16.4% | -12.3% | -48.4% | -5.3% |
| Utility | 29.6% | 1.8% | -11.3% | | | | | |
| Cost of goods sold [+] | 184.8 | 152.9 | 183.4 | 186.7 | 174.3 | 195.1 | 230.9 | 621.1 |
| Fuel costs | 0.1 | 0.5 | 1.7 | 2.5 | 17.5 | 9.0 | 17.4 | 259.8 |
| Maintenance and operations costs | 184.7 | 152.4 | 181.7 | 184.2 | 156.8 | 186.1 | 213.5 | 361.3 |
| Gross profit | 676.6 | 514.7 | 461.6 | 533.9 | 569.5 | 443.9 | 497.7 | 790.4 |
| Gross margin | 78.5% | 77.1% | 71.6% | 74.1% | 76.6% | 69.5% | 68.3% | 56.0% |
| Selling, general and administrative [+] | 85.3 | 82.1 | 79.4 | 77.9 | 73.5 | 77.1 | 68.4 | 87.0 |
| General and administrative | 85.3 | 82.1 | 79.4 | 77.9 | 73.5 | 77.1 | 68.4 | 87.0 |
| Other operating expenses | 461.4 | 271.2 | 218.4 | 208.7 | 297.9 | 171.5 | 163.6 | 361.7 |
| EBITDA [+] | 129.9 | 161.4 | 164.1 | 228.1 | 175.2 | 226.1 | 324.4 | 345.9 |
| EBITDA growth | -19.5% | -1.6% | -28.1% | 30.2% | -22.5% | -30.3% | -6.2% | -8.8% |
| EBITDA margin | 15.1% | 24.2% | 25.4% | 31.7% | 23.6% | 35.4% | 44.5% | 24.5% |
| Depreciation and amortization | 80.0 | 76.1 | 73.6 | 53.1 | 50.2 | 106.9 | 132.3 | 138.8 |
| EBIT [+] | 49.9 | 85.3 | 90.5 | 175.0 | 125.0 | 119.2 | 192.1 | 207.1 |
| EBIT growth | -41.5% | -5.7% | -48.3% | 40.0% | 4.9% | -37.9% | -7.2% | -13.1% |
| EBIT margin | 5.8% | 12.8% | 14.0% | 24.3% | 16.8% | 18.7% | 26.4% | 14.7% |
| Non-recurring items [+] | 0.6 | | 1.4 | 20.1 | -10.5 | 14.0 | 73.1 | 317.0 |
| Asset impairment | | | | | 2.8 | | 23.9 | 317.0 |
| Loss (gain) on sale of assets | | | 6.1 | 20.1 | -1.6 | 14.0 | 49.2 | |
| Interest expense, net [+] | 67.8 | 62.9 | 71.3 | 82.2 | 98.0 | 110.0 | 107.4 | 119.6 |
| Interest expense | 67.8 | 62.9 | 71.3 | 82.2 | 98.0 | 110.0 | 107.4 | 119.8 |
| Interest income | | | | | | | | 0.2 |
| Other income (expense), net [+] | 4.2 | | -29.7 | -41.2 | -5.6 | -1.7 | 0.8 | -1.9 |
| Gain (loss) on debt retirement | -0.1 | | -31.7 | -44.9 | -6.5 | -3.3 | -3.1 | -2.1 |
| Other | 4.3 | | 2.0 | 3.7 | 0.9 | 1.6 | 3.9 | 0.2 |
| Pre-tax income | -14.3 | 22.4 | -11.9 | 31.5 | 31.9 | -6.5 | 12.4 | -231.4 |
| Income taxes | -9.6 | -0.7 | -10.9 | -26.5 | 0.7 | -5.0 | -2.4 | 20.0 |
| Tax rate | 67.1% | | 91.6% | | 2.2% | 76.9% | | |
| Net income | -4.7 | 22.1 | -1.0 | 105.4 | 70.1 | -94.6 | -485.2 | -239.0 |
| Net margin | -0.5% | 3.3% | -0.2% | 14.6% | 9.4% | -14.8% | -66.6% | -16.9% |
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| EBIT is a non-GAAP figure that excludes all non-recurring expenses: restructuring costs, asset impairments, IPR&D writeoffs, and other unusual charges. |