| 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 | -19.4 | -19.1 | -14.4 | -9.4 | -9.8 | -8.3 | -7.5 | -15.2 |
| Depreciation and amortization [+] | 0.3 | 0.8 | 0.7 | 0.8 | 0.9 | 0.9 | 1.1 | 0.9 |
| Depreciation | 0.0 | 0.7 | 0.7 | 0.7 | 0.9 | 0.9 | 1.1 | 0.9 |
| Amortization of intangible assets | 0.2 | 0.1 | 0.1 | 0.1 | 0.0 | | | |
| Asset impairment charges | | 1.8 | 1.4 | | | | | |
| Stock-based compensation | 1.0 | 1.6 | 1.0 | 0.9 | 0.9 | 0.6 | 0.4 | 0.2 |
| Change in working capital [+] | 6.1 | 1.5 | 0.9 | -0.5 | -2.1 | 1.1 | 0.0 | -2.6 |
| Accounts receivable | | 0.0 | 0.0 | 0.2 | -1.1 | 0.0 | | |
| Inventories | | | | | | | | -1.3 |
| Other current assets | -0.2 | 1.6 | 0.7 | 0.0 | -0.3 | 0.0 | 0.0 | 0.1 |
| Accounts payable | 0.2 | -0.2 | -0.1 | -0.2 | 0.2 | 0.6 | -0.3 | -0.2 |
| Accrued expenses | 0.4 | 0.0 | 0.0 | -0.7 | -0.9 | 0.6 | 0.3 | -1.1 |
| Other | 5.7 | | 0.2 | 0.2 | | | | |
| Other operating activities | -4.0 | -0.4 | 0.0 | -0.8 | -0.5 | -2.3 | -1.4 | 0.6 |
| Cash from operations | -16.1 | -14.0 | -10.4 | -9.1 | -10.6 | -7.9 | -7.4 | -16.1 |
| |
| Capital expenditures [+] | -0.1 | 0.0 | 0.0 | -0.1 | -0.1 | 0.0 | -0.2 | -0.2 |
| Purchases of property and equipment | -0.1 | 0.0 | 0.0 | -0.1 | -0.1 | 0.0 | -0.2 | -0.2 |
| Sales of property and equipment | 3.9 | 0.2 | | | | | | |
| Purchases of intangible assets | -0.2 | -0.6 | -0.6 | -0.3 | -0.1 | 0.0 | -0.3 | -0.3 |
| Sales of short-term investments, net [+] | 7.4 | -0.2 | -8.6 | -5.8 | | 2.8 | 3.4 | 6.8 |
| Purchases of short-term investments | -2.7 | -22.5 | -18.6 | -5.8 | | | | |
| Sales of short-term investments | 10.1 | 22.3 | 10.0 | | | 2.8 | 3.4 | 6.8 |
| Other cash from investing | | | | | 0.2 | | | |
| Cash from investing | 11.0 | -0.6 | -9.2 | -6.1 | 0.1 | 2.7 | 2.9 | 6.4 |
| |
| Issuance of common stock, net | 0.1 | 13.0 | 61.2 | 15.3 | 5.1 | 2.4 | 4.7 | 9.7 |
| Financing costs | | | | | -0.4 | -0.1 | | |
| Other cash from financing | | -4.9 | -4.7 | 1.1 | 3.9 | 1.7 | 0.0 | 0.0 |
| Cash from financing | 0.1 | 8.2 | 56.6 | 16.4 | 9.4 | 4.2 | 4.8 | 9.7 |
| |
| Free cash flow | -16.2 | -14.0 | -10.4 | -9.1 | -10.7 | -8.0 | -7.5 | -16.3 |
| Per share (diluted) | ($0.33) | ($0.29) | ($0.33) | ($2.51) | ($10.65) | ($0.28) | ($0.35) | ($0.83) |
| |
| Cash paid for interest | | | | | | 0.1 | | 0.0 |