| In millions, except per share items | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | 10-K/A | 10-K/A | 10-K/A | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 0.0 | 0.0 | 0.0 | 10.4 | -34.6 | 11.0 | -0.8 | -23.3 |
| Depreciation and amortization | 0.4 | 0.4 | 0.4 | 0.4 | 0.5 | 0.5 | 0.5 | 0.5 |
| Asset impairment charges | | | 0.1 | | | 0.1 | 0.3 | 1.9 |
| Stock-based compensation | 0.8 | 1.1 | 0.9 | 0.8 | 1.0 | 1.2 | 1.1 | 0.8 |
| Tax benefit from stock-based compensation | | | | | 0.0 | -0.1 | -0.1 | |
| Deferred taxes | -0.3 | 2.3 | -11.1 | | 16.8 | -11.6 | 1.6 | 4.2 |
| Change in working capital | 93.7 | -7.2 | 2.6 | 3.4 | 0.3 | 0.2 | -4.5 | 2.4 |
| Other | 93.7 | -7.2 | 2.6 | 3.4 | 0.3 | 0.2 | -4.5 | 2.4 |
| Other operating activities | -84.5 | 20.5 | 24.4 | -4.5 | 20.4 | 0.5 | 10.5 | 49.1 |
| Cash from operations | 10.2 | 17.0 | 17.3 | 10.6 | 4.3 | 1.9 | 8.8 | 35.6 |
| |
| Capital expenditures [+] | -0.3 | -0.5 | -0.4 | -0.3 | -0.6 | -0.6 | -0.3 | -0.6 |
| Purchases of property and equipment | -0.3 | -0.5 | -0.4 | -0.3 | -0.6 | -0.6 | -0.3 | -0.6 |
| Sales of property and equipment | 0.6 | 0.1 | 0.0 | 0.0 | | 0.0 | 0.1 | 0.1 |
| Sales of short-term investments, net [+] | -9.6 | 4.5 | 9.7 | -3.0 | | 8.1 | 7.5 | 18.7 |
| Purchases of short-term investments | -22.7 | -5.0 | -5.2 | -3.4 | | -0.3 | -1.9 | -1.2 |
| Sales of short-term investments | 13.1 | 9.5 | 15.0 | 0.4 | | 8.4 | 9.4 | 19.9 |
| Other cash from investing | -98.5 | -42.8 | -33.4 | -112.3 | -91.7 | -21.9 | -52.7 | -40.1 |
| Cash from investing | -107.9 | -38.7 | -24.0 | -115.5 | -92.3 | -14.4 | -45.4 | -22.0 |
| |
| Issuance of common stock, net | | | | | | | | 15.0 |
| Option exercises | 0.1 | 0.6 | 0.4 | 1.2 | 0.5 | 1.5 | 1.2 | 0.3 |
| Other cash from financing | 163.9 | 54.7 | -3.4 | 165.5 | 113.4 | -49.3 | 108.0 | -49.6 |
| Cash from financing | 163.8 | 54.1 | -3.7 | 164.3 | 112.9 | -50.8 | 106.8 | -34.9 |
| |
| Free cash flow | 9.9 | 16.5 | 16.9 | 10.3 | 3.7 | 1.4 | 8.4 | 35.0 |
| Per share (diluted) | $416.47 | $699.22 | $718.92 | $0.44 | $0.16 | $0.07 | $0.44 | $1.92 |
| |
| Cash paid for interest | 8.8 | 16.1 | 13.7 | 7.6 | 5.5 | 5.2 | 7.9 | 4.9 |