| In millions, except per share items | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 69.7 | 112.9 | 78.8 | 69.9 | 113.0 | 39.6 | 86.2 | 20.7 |
| Depreciation and amortization [+] | 197.4 | 209.3 | 229.2 | 221.3 | 203.9 | 187.2 | 168.1 | 129.9 |
| Depreciation | 197.4 | 209.3 | 229.2 | 221.3 | 202.5 | 185.8 | 166.7 | 128.6 |
| Amortization of intangible assets | | | | | 1.4 | 1.4 | 1.4 | 1.4 |
| Asset impairment charges | 2.7 | 43.6 | 25.2 | 9.8 | 9.0 | | | |
| Stock-based compensation | 6.9 | 8.3 | 7.6 | 12.0 | 10.5 | 8.8 | 20.2 | 6.4 |
| Deferred taxes | -8.1 | 1.0 | 1.0 | -26.0 | 8.7 | -0.5 | -11.6 | 2.4 |
| Change in working capital [+] | 14.7 | 16.3 | 5.7 | -3.1 | 23.8 | -1.4 | 23.6 | -5.0 |
| Accounts receivable | 5.7 | 2.2 | -0.9 | -2.7 | 8.3 | -5.0 | -2.9 | -2.9 |
| Other | 9.0 | 14.0 | 6.6 | -0.4 | 15.5 | 3.7 | 26.5 | -2.1 |
| Other operating activities | 116.7 | 58.4 | 99.1 | 138.4 | 59.9 | 136.8 | 24.8 | 46.6 |
| Cash from operations | 400.0 | 449.9 | 446.5 | 422.4 | 428.9 | 370.5 | 311.3 | 201.1 |
| |
| Capital expenditures [+] | -192.5 | -171.4 | -166.4 | -225.3 | -204.7 | -173.2 | -172.5 | -271.5 |
| Purchases of property and equipment | -182.4 | -158.7 | -166.4 | -225.3 | -204.7 | -173.2 | -172.5 | -271.5 |
| Capitalized product costs | -10.1 | -12.7 | | | | | | |
| Sales of property and equipment | | 309.1 | 63.9 | | 277.1 | 3.2 | | |
| Purchases of intangible assets | -9.1 | -3.0 | | | | | | |
| Acquisitions | | | | | | | -16.4 | -128.3 |
| Other cash from investing | -58.2 | -28.3 | 3.3 | 3.1 | -6.1 | -12.2 | | 175.9 |
| Cash from investing | -259.8 | 106.3 | -99.1 | -222.3 | 66.3 | -182.2 | -165.3 | -223.8 |
| |
| Cash dividends paid | -67.2 | -45.8 | -56.1 | -74.2 | -12.3 | | | -832.9 |
| Issuance of common stock, net | -130.7 | -85.4 | -62.3 | -139.9 | | | 649.8 | |
| Financing costs | -20.7 | | | -34.5 | 11.5 | -5.2 | -9.9 | -64.6 |
| Other cash from financing | 95.3 | -272.4 | -184.0 | -372.4 | -219.4 | -132.4 | -848.6 | 795.9 |
| Cash from financing | -81.9 | -403.6 | -302.5 | -551.9 | -243.2 | -127.2 | -189.0 | 27.6 |
| |
| Free cash flow | 217.6 | 291.1 | 280.1 | 197.1 | 224.2 | 197.2 | 138.8 | -70.4 |
| Per share (diluted) | $1.11 | $1.47 | $1.45 | $0.98 | $1.10 | $0.96 | | ($0.41) |
| |
| Cash paid for interest | 108.5 | 118.5 | 124.0 | 117.5 | 120.2 | 125.3 | 201.2 | 196.4 |
| Cash paid for income taxes | 39.6 | 38.6 | 55.7 | 78.9 | 69.8 | 36.4 | 1.2 | 11.3 |