| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Service revenue | 0.8 | 0.2 | | | | | 0.3 | 2.9 |
| Service revenue growth | 250.4% | | | | | -100.0% | -89.1% | -32.7% |
| Operating expenses: | | | | | | | | |
| Cost of service revenue | 0.8 | 0.2 | | | | | | |
| Research and development | 21.0 | 21.6 | 25.4 | 25.5 | 20.1 | 20.5 | 20.4 | 11.0 |
| General and administrative | 10.5 | 11.2 | 11.8 | 9.4 | 8.2 | 8.2 | 6.3 | 4.4 |
| Impairment loss | | | | 0.5 | 0.1 | | | |
| Total operating expenses | 32.3 | 33.0 | 37.2 | | | | | |
| Loss from operations | -31.5 | -32.8 | -37.2 | -35.4 | -28.4 | -28.6 | -26.4 | -12.6 |
| Operating margin | -4016.8% | -14624.1% | | | | | -8424.3% | -440.8% |
| |
| Other income (expense): | | | | | | | | |
| Interest income | 0.0 | 0.0 | 0.2 | 0.4 | 0.1 | | | |
| Interest expense | -0.2 | -0.7 | -0.5 | -0.4 | -0.8 | -1.2 | -1.6 | -1.8 |
| Other income (expense), net | 1.8 | 0.1 | -0.1 | 0.0 | 0.0 | 0.0 | -0.1 | -0.1 |
| Loss before provision for income taxes | -29.9 | -33.4 | -37.6 | -35.4 | -29.1 | -29.8 | | |
| Net loss | -29.9 | -33.4 | -37.6 | -35.4 | -29.1 | -29.8 | -28.4 | -14.2 |
| |
| Net loss per common share - basic (in USD per share) | ($0.27) | ($0.49) | ($2.29) | ($3.74) | ($16.82) | ($43.36) | ($2.49) | ($2.78) |
| Net loss per common share - diluted (in USD per share) | ($0.27) | ($0.49) | ($2.29) | ($3.74) | ($16.82) | ($43.36) | ($2.49) | ($2.78) |
| |
| Weighted-average common shares used in computing net loss per common share – basic | 112.1 | 67.9 | 16.4 | 9.5 | 1.7 | 0.7 | 11.4 | 5.1 |
| Weighted-average common shares used in computing net loss per common share – diluted | 112.1 | 67.9 | 16.4 | 9.5 | 1.7 | 0.7 | 11.4 | 5.1 |
| |
| Revenue from Contract with Customer, Product and Service [Extensible List] | | | | | | | | |
| Cost, Product and Service [Extensible List] | | | | | | | | |