| 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 |
| Revenue | 396.0 | 321.4 | 204.5 | 205.2 | 291.0 | 275.0 | 57.2 | 299.6 |
| Revenue growth | 23.2% | 57.2% | -0.4% | -29.5% | 5.8% | 380.9% | -80.9% | -12.4% |
| Cost of goods sold | | | | | | | | |
| Gross (loss) profit | 29.0 | 23.5 | 31.3 | 74.1 | 73.4 | 20.3 | 46.9 | 57.0 |
| Gross margin | 7.3% | 7.3% | 15.3% | 36.1% | 25.2% | 7.4% | 81.9% | 19.0% |
| |
| Selling, general, and administrative expenses | | | | | | | | |
| Compensation expense | 3.5 | 2.6 | 2.8 | 3.0 | 3.8 | 4.2 | 4.9 | 5.0 |
| Other expense | 3.9 | 3.9 | 2.6 | 1.9 | 1.9 | 2.0 | 2.2 | 2.2 |
| Research and development expenses | 3.4 | 3.5 | 3.0 | 3.2 | 3.5 | 3.7 | 2.7 | 2.7 |
| Total operating expenses | 11.4 | 10.6 | 9.0 | 8.8 | 10.0 | 10.4 | 10.3 | 10.1 |
| (Loss) income from operations | 17.5 | 12.9 | 22.3 | 65.3 | 63.4 | 9.9 | 36.5 | 47.0 |
| Operating margin | 4.4% | 4.0% | 10.9% | 31.8% | 21.8% | 3.6% | 63.9% | 15.7% |
| Interest and dividend income | 4.9 | 3.1 | 5.6 | 10.1 | 9.2 | 7.8 | 6.2 | 5.1 |
| Interest expense | -0.1 | -0.1 | -0.2 | -0.2 | -0.2 | -0.2 | -0.2 | -0.1 |
| Gain (loss) on marketable securities | -8.5 | -0.1 | -4.4 | 4.6 | -12.0 | -0.7 | -1.3 | 0.1 |
| Other expense | 0.0 | 0.1 | 8.3 | 0.0 | -0.3 | -0.2 | -0.4 | -0.2 |
| Other income (expense) | -3.8 | 3.0 | 9.4 | 14.5 | -3.3 | 6.8 | 4.3 | 4.9 |
| (Loss) income before taxes | 13.7 | 15.9 | 31.8 | 79.8 | 60.2 | 16.6 | 40.8 | |
| Income tax provision (benefit) | -1.5 | -10.3 | -14.8 | -8.4 | 7.0 | -6.9 | -15.5 | 5.4 |
| Net (loss) income | 15.2 | 26.3 | 46.6 | 88.2 | 53.2 | 23.5 | 56.3 | 46.4 |
| |
| (Loss) earnings per common share | | | | | | | | |
| Basic (in dollars per share) | $0.35 | $0.60 | $1.06 | $2.02 | $1.22 | $0.54 | $1.29 | $1.06 |
| Diluted (in dollars per share) | $0.35 | $0.60 | $1.06 | $2.02 | $1.22 | $0.54 | $1.29 | $1.06 |
| |
| Weighted average shares outstanding | | | | | | | | |
| Basic (in shares) | 43.8 | 43.8 | 43.7 | 43.7 | 43.7 | 43.7 | 43.5 | 43.4 |
| Diluted (in shares) | 43.8 | 43.8 | 43.7 | 43.7 | 43.7 | 43.7 | 43.5 | 43.4 |
| |
| Comprehensive (loss) income | | | | | | | | |
| Net (loss) income | 15.2 | 26.3 | 46.6 | 88.2 | 53.2 | 23.5 | 56.3 | 46.4 |
| Income tax effect | 0.0 | 0.0 | 0.0 | -0.1 | 0.0 | -2.6 | -1.2 | 1.3 |
| Comprehensive (loss) income | 15.0 | 26.2 | 46.5 | 88.5 | 53.0 | 28.4 | 57.8 | 44.2 |