| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | S-1/A |
| Net income | 13.0 | 11.1 | 10.0 | -14.1 | 5.7 | 2,715.3 |
| Depreciation and amortization | 1.1 | 1.1 | 1.0 | 0.9 | 0.9 | |
| Stock-based compensation | 1.5 | 1.8 | 0.8 | | | |
| Deferred taxes | 1.0 | 2.3 | 0.0 | -6.2 | 0.9 | |
| Change in working capital [+] | 0.7 | -24.0 | 0.8 | 1.9 | -1.0 | |
| Other current assets | -2.1 | -3.0 | 1.0 | 0.3 | -0.4 | |
| Other | 2.9 | -21.0 | -0.2 | 1.6 | -0.6 | |
| Other operating activities | 0.8 | -2.0 | 4.0 | 27.7 | 1.9 | |
| Cash from operations | 18.2 | -9.6 | 16.6 | 10.1 | 8.5 | |
| |
| Capital expenditures [+] | -0.4 | -0.6 | -1.9 | -1.0 | -1.3 | |
| Purchases of property and equipment | -0.4 | -0.6 | -1.9 | -1.0 | -1.3 | |
| Sales of property and equipment | | | 0.0 | | | |
| Purchases of short-term investments, net | 9.6 | -121.7 | -39.5 | -75.5 | 19.7 | |
| Purchases of short-term investments | -22.5 | -188.8 | -167.4 | -164.3 | | |
| Sales of short-term investments | 32.2 | 67.1 | 127.8 | 88.8 | 19.7 | |
| Other cash from investing | -125.4 | -89.9 | -47.9 | -30.4 | -119.9 | |
| Cash from investing | -116.1 | -212.2 | -89.3 | -106.8 | -101.5 | |
| |
| Cash dividends paid | -4.4 | -9.3 | -1.8 | | | |
| Repurchase of common stock, net | -9.9 | -11.9 | -9.1 | | | |
| Option exercises | | 0.1 | | | | |
| Other cash from financing | 105.1 | 217.4 | 91.8 | 122.3 | 91.9 | |
| Cash from financing | 90.8 | 196.1 | 80.9 | 122.3 | 91.9 | |
| |
| Free cash flow | 17.8 | -10.2 | 14.7 | 9.1 | 7.1 | |
| Per share (diluted) | $1.48 | ($0.80) | $1.10 | $0.82 | | |
| |
| Cash paid for interest | 9.1 | 7.6 | 9.5 | 11.4 | 7.4 | |