| 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 | S-1/A |
| Net income | 33.3 | 28.8 | 13.1 | 16.8 | 14.3 | 9.2 | 7.4 | 6.0 |
| Depreciation and amortization | 1.4 | 1.3 | 1.3 | 1.1 | 1.0 | 1.0 | 1.1 | |
| Stock-based compensation | 1.2 | 0.6 | 1.1 | 1.5 | 1.0 | 0.7 | 1.2 | |
| Deferred taxes | 1.1 | -2.3 | -2.3 | 0.2 | 0.2 | 0.1 | | |
| Change in working capital | -3.8 | 2.9 | -1.9 | -115.1 | -2.6 | 3.9 | 2.6 | |
| Other | -3.8 | 2.9 | -1.9 | -115.1 | -2.6 | 3.9 | 2.6 | |
| Other operating activities | 50.6 | -59.6 | -16.1 | 114.5 | 16.7 | -17.0 | -1.7 | |
| Cash from operations | 83.7 | -28.3 | -4.9 | 19.0 | 30.6 | -2.1 | 10.6 | |
| |
| Capital expenditures | -1.4 | -1.1 | -0.6 | -1.7 | -1.2 | -0.4 | -0.3 | |
| Purchases of property and equipment | -1.4 | -1.1 | -0.6 | -1.7 | -1.2 | -0.4 | -0.3 | |
| Purchases of short-term investments, net | -83.6 | -62.4 | -34.9 | -0.4 | -16.8 | -6.5 | 8.1 | |
| Purchases of short-term investments | -115.8 | -98.4 | -65.2 | -15.0 | -23.4 | -12.7 | | |
| Sales of short-term investments | 32.2 | 35.9 | 30.3 | 14.5 | 6.6 | 6.2 | 8.1 | |
| Other cash from investing | -376.7 | -222.5 | -111.5 | -115.9 | -128.3 | -74.7 | -167.9 | |
| Cash from investing | -461.8 | -286.0 | -147.1 | -118.0 | -146.3 | -81.7 | -160.1 | |
| |
| Cash dividends paid | -6.7 | -5.1 | -4.3 | -3.2 | | | | |
| Issuance of common stock, net | | 0.0 | -8.1 | -5.4 | 22.6 | | | |
| Option exercises | 0.6 | 0.1 | 0.4 | 0.6 | 0.7 | 0.4 | 0.2 | |
| Other cash from financing | 352.8 | 328.7 | 185.0 | 116.5 | 108.3 | 127.4 | 132.4 | |
| Cash from financing | 345.6 | 323.5 | 172.3 | 107.4 | 130.2 | 126.9 | 132.2 | |
| |
| Free cash flow | 82.3 | -29.4 | -5.5 | 17.2 | 29.4 | -2.6 | 10.3 | |
| Per share (diluted) | $5.40 | ($1.94) | ($0.36) | $1.08 | $1.89 | ($0.19) | $0.78 | |
| |
| Cash paid for interest | 9.1 | 3.6 | 10.0 | 13.5 | 7.8 | 4.5 | 3.4 | |