| In millions, except per share items | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | S-1/A |
| Net income | -124.5 | -226.8 | 7.6 | 58.1 | 36.1 | 40.4 | -24.4 | -1.6 |
| Depreciation and amortization | 7.6 | 7.3 | 6.2 | 5.3 | 2.5 | 1.8 | 1.7 | 1.4 |
| Asset impairment charges | 3.1 | 6.2 | 7.4 | -0.3 | | | | |
| Stock-based compensation | 12.0 | 16.0 | 21.6 | 21.9 | 15.3 | 6.3 | 2.8 | 1.7 |
| Tax benefit from stock-based compensation | | | | | -21.4 | -2.7 | | |
| Deferred taxes | | 23.2 | -5.6 | -4.9 | -0.7 | -12.0 | | |
| Change in working capital [+] | 36.4 | -13.2 | 20.1 | 25.0 | 18.5 | -10.4 | 0.4 | -6.0 |
| Accounts receivable | 8.9 | -0.9 | 26.6 | -23.8 | -7.8 | -13.2 | -3.1 | |
| Inventories | 2.3 | 2.3 | 7.6 | -3.3 | -23.6 | -7.4 | -0.4 | -6.0 |
| Other current assets | 9.5 | -14.5 | -1.7 | 1.3 | -3.0 | -0.4 | -0.1 | |
| Deferred revenues | | | | | | -3.8 | 3.8 | |
| Other | 15.8 | -0.1 | -12.4 | 50.7 | 52.8 | 14.4 | 0.2 | |
| Other operating activities | 9.4 | 126.6 | 1.6 | -2.7 | 0.4 | 0.9 | 5.9 | -10.9 |
| Cash from operations | -56.0 | -60.7 | 58.9 | 102.3 | 50.6 | 24.2 | -13.6 | -15.4 |
| |
| Capital expenditures | -6.1 | -16.7 | -10.6 | -13.8 | -22.2 | -5.1 | -1.0 | -0.6 |
| Purchases of property and equipment | -6.1 | -16.7 | -10.6 | -13.8 | -22.2 | -5.1 | -1.0 | -0.6 |
| Sales of short-term investments | 121.2 | 130.9 | 104.0 | 62.1 | 8.2 | | | |
| Sales of short-term investments | 121.2 | 130.9 | 104.0 | 62.1 | 8.2 | | | |
| Other cash from investing | -61.7 | -132.1 | -115.4 | -138.5 | -56.2 | -0.4 | | |
| Cash from investing | 53.4 | -17.8 | -22.0 | -90.2 | -70.3 | -5.5 | -1.0 | -0.6 |
| |
| Issuance of common stock, net | 1.0 | 1.3 | -13.8 | -13.8 | 2.0 | 33.3 | | 0.0 |
| Option exercises | 1.1 | 4.5 | 3.8 | 9.5 | 9.0 | 2.1 | 0.2 | |
| Other cash from financing | 2.2 | 9.0 | 5.9 | 32.6 | 39.4 | -4.9 | 15.1 | 16.0 |
| Cash from financing | 2.1 | 5.8 | -11.7 | 9.3 | 32.4 | 26.3 | 15.0 | 15.9 |
| |
| Free cash flow | -62.1 | -77.3 | 48.3 | 88.4 | 28.3 | 19.1 | -14.6 | -16.0 |
| Per share (diluted) | ($0.84) | ($1.06) | $0.65 | $1.17 | $0.39 | $0.33 | ($1.57) | ($20.38) |
| |
| Cash paid for interest | | | | | | | 0.1 | |
| Cash paid for income taxes | -13.4 | 2.1 | 10.7 | | | | | |