| 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 |
| Net income | -23.2 | -73.3 | 255.6 | 95.2 | 74.2 | -29.1 | -14.1 | -4.6 |
| Depreciation and amortization | 0.1 | 0.1 | 0.3 | 0.4 | 0.3 | 0.0 | 0.0 | |
| Asset impairment charges | | | 54.3 | | | | | |
| Stock-based compensation | 4.3 | 8.1 | 18.1 | 4.9 | 5.3 | 1.5 | 0.6 | 0.1 |
| Change in working capital [+] | -8.6 | -2.6 | -36.2 | 16.8 | -0.3 | 1.0 | 0.8 | 0.4 |
| Accounts receivable | | | | | | -0.8 | | |
| Inventories | 0.1 | 0.1 | -6.0 | -1.4 | | | | |
| Other current assets | | | -17.1 | 0.4 | -0.3 | -1.8 | -0.6 | 0.0 |
| Accounts payable | | | | | | 0.6 | 0.9 | |
| Accrued expenses | | | | | | 3.0 | 0.5 | 0.3 |
| Deferred revenues | | | | | | | | 0.0 |
| Other | -8.7 | -2.7 | -13.0 | 17.8 | 0.0 | 0.0 | 0.0 | |
| Other operating activities | -1.8 | 11.3 | -429.3 | -190.6 | -148.1 | -1.6 | 10.4 | |
| Cash from operations | -29.2 | -56.4 | -137.1 | -73.4 | -68.7 | -28.2 | -2.3 | -4.2 |
| |
| Capital expenditures [+] | 0.0 | 0.0 | -0.1 | -1.1 | -0.6 | 0.0 | 0.0 | 0.0 |
| Purchases of property and equipment | | | -0.1 | -1.1 | -0.6 | 0.0 | 0.0 | |
| Sales of property and equipment | | | | 0.0 | 0.0 | | | |
| Sales of short-term investments, net [+] | | 1.0 | 50.6 | 42.9 | -11.2 | 49.1 | 17.8 | |
| Purchases of short-term investments | | | | -45.0 | -77.7 | | | |
| Sales of short-term investments | | 1.0 | 50.6 | 87.9 | 66.5 | 49.1 | 17.8 | |
| Other cash from investing | 15.7 | | 38.6 | | | -64.1 | -55.3 | |
| Cash from investing | 15.7 | 1.0 | 89.1 | 41.9 | -11.8 | -15.1 | -37.5 | 0.0 |
| |
| Issuance of common stock, net | 1.5 | 76.0 | 61.6 | 13.7 | 91.5 | | | |
| Option exercises | | 0.5 | 0.3 | 0.4 | 0.0 | 0.0 | | 0.1 |
| Financing costs | | | | | | -0.9 | | |
| Other cash from financing | 0.2 | -35.7 | 0.5 | 34.6 | 0.9 | 48.7 | | 47.8 |
| Cash from financing | 1.7 | 39.8 | 61.8 | 48.0 | 92.4 | 49.5 | 0.0 | 47.7 |
| |
| Free cash flow | -29.2 | -56.4 | -137.2 | -74.5 | -69.2 | -28.2 | -2.3 | -4.2 |
| Per share (diluted) | ($9.17) | ($19.72) | ($4.23) | ($8.77) | ($10.71) | ($5.53) | ($0.46) | ($0.88) |
| |
| Cash paid for interest | | 2.4 | 3.9 | 0.8 | | | | |
| Cash paid for income taxes | | | | | 0.6 | | | |