| 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 | 54.8 | 29.3 | 26.2 | 17.7 | 10.5 | 7.1 | 7.8 | 6.0 |
| Depreciation and amortization [+] | 6.3 | 4.5 | 4.6 | 4.2 | 3.6 | 1.6 | 1.8 | 1.6 |
| Depreciation | 4.3 | 3.3 | 3.2 | 2.8 | 2.4 | 1.5 | 1.7 | 1.5 |
| Amortization of intangible assets | 2.0 | 1.2 | 1.4 | 1.4 | 1.2 | 0.1 | 0.1 | 0.1 |
| Stock-based compensation | 1.1 | 0.7 | 0.4 | 0.3 | 0.3 | 0.1 | 0.1 | 0.0 |
| Deferred taxes | 2.3 | 0.5 | -1.4 | 0.7 | 1.3 | 1.8 | -0.3 | 1.0 |
| Change in working capital [+] | -415.9 | 132.1 | -624.8 | -139.8 | -135.1 | -97.2 | -77.8 | -61.2 |
| Accounts receivable | -7.1 | 3.6 | -5.0 | 0.3 | -0.4 | -0.6 | -0.1 | -0.4 |
| Accrued expenses | 0.5 | -0.7 | -0.2 | -0.1 | 0.5 | 0.1 | 0.1 | 0.0 |
| Other | -409.4 | 129.2 | -619.6 | -140.0 | -135.3 | -96.7 | -77.8 | -60.8 |
| Other operating activities | 411.4 | -101.2 | 609.0 | 124.7 | 130.4 | 98.5 | 90.3 | 65.7 |
| Cash from operations | 60.0 | 65.9 | 14.1 | 7.8 | 11.0 | 11.9 | 21.8 | 13.2 |
| |
| Capital expenditures [+] | -4.2 | -3.5 | -3.7 | -3.9 | -9.0 | -6.9 | -0.8 | -1.5 |
| Purchases of property and equipment | -4.2 | -3.5 | -3.7 | -3.9 | -9.0 | -6.9 | -0.8 | -1.5 |
| Sales of property and equipment | 0.2 | 0.1 | 0.1 | 1.3 | | 2.2 | | |
| Sales of short-term investments, net [+] | -184.5 | -14.7 | 139.3 | 170.7 | 165.2 | 48.0 | -15.4 | 13.2 |
| Purchases of short-term investments | -214.0 | -65.2 | -78.5 | -20.4 | -24.8 | -16.0 | -142.9 | -35.9 |
| Sales of short-term investments | 29.5 | 50.5 | 217.9 | 191.1 | 190.0 | 64.0 | 127.5 | 49.1 |
| Other cash from investing | -516.2 | 187.5 | -724.6 | -195.1 | -134.4 | -207.1 | -70.7 | -50.7 |
| Cash from investing | -704.7 | 169.4 | -588.9 | -27.0 | 21.8 | -163.8 | -86.8 | -38.9 |
| |
| Cash dividends paid | -12.7 | -8.9 | -6.5 | -6.7 | -4.5 | -2.2 | -2.5 | -1.8 |
| Issuance of common stock, net | -3.0 | 70.1 | -1.8 | | | | | |
| Financing costs | | | | | | -0.1 | | -0.1 |
| Other cash from financing | -192.5 | 313.5 | 747.8 | 124.8 | -11.8 | 131.6 | 100.1 | 30.8 |
| Cash from financing | -208.2 | 374.8 | 739.5 | 118.1 | -16.3 | 129.4 | 97.6 | 29.1 |
| |
| Free cash flow | 55.7 | 62.4 | 10.4 | 3.9 | 2.0 | 5.0 | 21.1 | 11.7 |
| Per share (diluted) | $3.50 | $5.77 | $1.23 | $0.46 | $0.29 | $1.18 | $4.98 | $2.85 |
| |
| Cash paid for interest | 17.3 | 15.0 | 19.9 | 25.2 | 11.1 | 6.2 | 5.2 | 4.6 |