| 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 |
| | 20-F | 20-F | 20-F | 20-F | 20-F | 20-F | 20-F | 20-F |
| Net income | 175.2 | -139.0 | 199.4 | 131.2 | 299.0 | 121.3 | -83.4 | -87.7 |
| Depreciation and amortization [+] | 199.9 | 216.1 | 204.9 | 181.5 | 172.5 | 165.5 | 140.4 | 101.0 |
| Depreciation | 199.9 | 216.1 | 204.9 | 181.5 | 172.5 | 165.5 | 140.4 | 101.0 |
| Asset impairment charges | | 285.2 | | | | | | |
| Stock-based compensation | 17.5 | 6.4 | 4.5 | 8.3 | 14.6 | 4.8 | 3.3 | 2.7 |
| Change in working capital [+] | 8.4 | -5.7 | 4.9 | 21.2 | 13.6 | 6.8 | 2.3 | 8.3 |
| Accounts receivable | 16.6 | -21.7 | -0.3 | -9.6 | -4.6 | 5.8 | 0.9 | |
| Deferred revenues | -7.4 | 4.8 | -10.1 | 3.2 | -1.2 | -2.7 | 6.3 | 0.9 |
| Other | -0.8 | 11.2 | 15.4 | 27.6 | 19.4 | 3.8 | -5.0 | 7.4 |
| Other operating activities | -77.9 | -51.8 | -77.9 | | | | | |
| Cash from operations | 323.2 | 311.1 | 335.9 | 343.0 | 327.7 | 311.2 | 239.9 | 153.6 |
| |
| Capital expenditures [+] | -338.5 | -343.6 | -712.7 | -524.3 | -255.6 | -210.6 | -623.3 | -715.6 |
| Purchases of property and equipment | -338.5 | -343.6 | -712.7 | -524.3 | -255.6 | -209.6 | -621.9 | -715.6 |
| Capitalized product costs | | | | | | -1.0 | -1.3 | |
| Sales of property and equipment | 37.1 | 32.1 | | | | | | |
| Purchases of intangible assets | | | | | | | | -1.8 |
| Other cash from investing | 17.6 | 45.9 | -4.0 | -167.0 | -39.6 | -18.9 | -2.0 | -65.0 |
| Cash from investing | -283.9 | -265.6 | -716.6 | -691.2 | -295.2 | -229.6 | -625.3 | -782.4 |
| |
| Cash dividends paid | -61.8 | -148.6 | -105.7 | -62.3 | -44.4 | -51.8 | -34.4 | -23.0 |
| Issuance of common stock, net | 119.0 | 87.7 | -13.9 | 4.2 | 64.2 | -172.8 | | |
| Financing costs | -8.2 | -13.0 | -17.4 | -17.4 | -23.3 | -3.8 | -10.0 | -7.4 |
| Other cash from financing | -219.4 | 154.8 | 496.7 | 114.3 | 19.3 | 39.4 | 856.7 | 545.3 |
| Cash from financing | -154.1 | 106.9 | 394.5 | 73.6 | 62.5 | -181.4 | 832.3 | 529.7 |
| |
| Free cash flow | -15.3 | -32.5 | -376.8 | -181.3 | 72.1 | 101.6 | -382.1 | -562.1 |
| Per share (diluted) | ($0.13) | ($0.32) | ($3.80) | ($1.94) | $0.82 | $1.55 | ($5.54) | ($8.24) |