| In millions, except per share items | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | -79.1 | 18.2 | 39.4 | 39.3 | 40.8 | 38.5 | 19.7 | 1.4 |
| Depreciation and amortization | 168.1 | 171.6 | 145.8 | 123.1 | 108.6 | 83.1 | 63.4 | 43.3 |
| Asset impairment charges | 94.1 | | 5.1 | | | | | |
| Stock-based compensation | 14.6 | 18.3 | 17.6 | 17.7 | 16.1 | 10.3 | 7.0 | 1.2 |
| Tax benefit from stock-based compensation | | -0.1 | -1.6 | -2.6 | -3.9 | -8.6 | -2.3 | |
| Deferred taxes | 14.5 | -14.0 | -13.0 | -14.2 | -3.3 | 1.5 | 5.6 | 7.1 |
| Change in working capital [+] | -31.7 | -12.1 | -22.7 | 22.8 | 14.1 | -5.2 | 15.6 | 52.4 |
| Accounts receivable | 14.1 | -39.7 | 10.9 | 14.0 | -13.3 | -9.0 | -3.5 | -5.5 |
| Other current assets | -21.2 | 10.3 | -17.7 | 3.6 | -9.4 | 8.7 | -12.1 | -6.0 |
| Accounts payable | -1.1 | 0.9 | 0.7 | -0.1 | -0.2 | -0.3 | 0.3 | -0.3 |
| Accrued expenses | -0.1 | 1.7 | 4.6 | 6.9 | 3.6 | -0.7 | 5.2 | 6.6 |
| Deferred revenues | -23.5 | 14.7 | -21.3 | -1.6 | 33.4 | -4.0 | 25.7 | 57.7 |
| Other operating activities | 1.1 | 5.3 | 2.6 | 5.4 | | | | 14.7 |
| Cash from operations | 181.5 | 187.3 | 173.2 | 191.5 | 212.5 | 91.4 | 120.3 | 120.1 |
| |
| Capital expenditures [+] | -107.7 | -120.4 | -135.0 | -138.5 | -130.0 | -89.1 | -103.1 | -72.6 |
| Purchases of property and equipment | -1.3 | -3.7 | -2.2 | -1.5 | -2.9 | -1.7 | -2.0 | -0.5 |
| Capitalized product costs | -106.3 | -116.7 | -132.8 | -137.0 | -127.1 | -87.4 | -101.2 | -72.1 |
| Purchases of intangible assets | | | | | | -0.1 | -0.1 | |
| Acquisitions | | -228.5 | -0.4 | -2.3 | | -45.8 | -3.3 | |
| Purchases of short-term investments, net | 70.9 | 135.1 | 2.2 | -49.9 | -62.5 | 2.4 | -124.2 | |
| Purchases of short-term investments | -39.5 | -71.0 | -273.9 | -224.5 | -210.7 | -185.6 | -202.4 | |
| Sales of short-term investments | 110.4 | 206.1 | 276.0 | 174.7 | 148.2 | 188.0 | 78.2 | |
| Other cash from investing | 0.2 | 0.3 | -1.6 | -23.8 | -1.7 | 0.8 | 0.2 | 0.3 |
| Cash from investing | -36.5 | -213.5 | -134.9 | -214.4 | -194.2 | -131.6 | -230.6 | -72.4 |
| |
| Cash dividends paid | -2.5 | | | | | | | |
| Issuance of common stock, net | -8.3 | -60.1 | -26.2 | | | | 184.3 | -3.5 |
| Option exercises | 6.0 | 3.8 | 5.0 | 3.2 | 5.2 | 3.2 | 3.0 | 0.1 |
| Financing costs | | -2.0 | | | | | | |
| Other cash from financing | -90.4 | 93.9 | 9.7 | 4.0 | 13.4 | 10.4 | -11.0 | -26.5 |
| Cash from financing | -107.1 | 32.0 | -21.4 | 0.8 | 8.3 | 7.1 | 170.4 | -30.0 |
| |
| Free cash flow | 180.2 | 183.6 | 171.1 | 190.0 | 209.6 | 89.7 | 118.4 | 119.6 |
| Per share (diluted) | $1.50 | $1.31 | $0.69 | $0.97 | $1.54 | $0.04 | $0.48 | $6.63 |
| |
| Cash paid for interest | 2.9 | 2.6 | | | | 0.1 | 1.2 | 3.7 |
| Cash paid for income taxes | 7.9 | 15.1 | 24.0 | 15.1 | 17.8 | 4.7 | 9.0 | 6.1 |