| In millions, except per share items | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 | Dec-31-09 | Dec-31-08 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 9.6 | 28.8 | 102.7 | 9.8 | -8.1 | 1.2 | 9.2 | 30.4 |
| Depreciation and amortization [+] | 135.9 | 143.8 | 138.6 | 107.9 | 97.3 | 89.1 | 46.9 | 45.3 |
| Depreciation | 68.4 | 72.0 | 70.5 | 56.1 | 51.0 | 45.5 | 46.9 | 45.3 |
| Amortization of intangible assets | 0.0 | 0.3 | 0.3 | -0.5 | -0.3 | 0.2 | | |
| Stock-based compensation | | | | | | | 0.0 | 0.1 |
| Change in working capital [+] | 7.3 | -27.1 | -12.8 | -8.4 | -4.9 | 2.5 | -1.1 | -5.5 |
| Restricted cash | | 0.1 | 0.1 | 1.3 | 1.4 | -0.4 | | |
| Other | 7.3 | -27.2 | -12.8 | -9.7 | -6.3 | 2.8 | -1.1 | -5.5 |
| Other operating activities | -55.5 | -63.1 | -159.5 | -40.4 | -21.0 | -33.3 | 16.0 | -3.7 |
| Cash from operations | 97.4 | 82.5 | 69.0 | 69.0 | 63.3 | 59.5 | 71.1 | 66.7 |
| |
| Capital expenditures | -69.9 | -30.4 | -20.5 | -24.4 | -40.8 | -23.5 | 0.0 | 0.0 |
| Purchases of property and equipment | -69.9 | -30.4 | -20.5 | -24.4 | -40.8 | -23.5 | | |
| Sales of short-term investments, net [+] | | | 7.8 | 4.5 | -3.0 | 2.8 | | |
| Purchases of short-term investments | | | | -2.7 | -5.6 | -1.9 | | |
| Sales of short-term investments | | | 7.8 | 7.3 | 2.6 | 4.7 | | |
| Other cash from investing | 36.6 | -78.2 | -103.0 | -162.7 | -58.1 | -8.1 | 6.1 | -110.6 |
| Cash from investing | -33.3 | -108.6 | -115.7 | -182.6 | -101.9 | -28.7 | 6.1 | -110.6 |
| |
| Cash dividends paid | -73.2 | -67.0 | -62.9 | -58.5 | -51.3 | -48.9 | | |
| Option exercises | | | | | | 2.6 | | |
| Financing costs | -0.3 | -2.0 | -0.3 | -3.1 | -3.2 | -7.3 | | |
| Other cash from financing | -0.1 | 98.3 | 102.1 | 179.9 | 80.9 | 20.2 | -75.6 | 30.8 |
| Cash from financing | -72.9 | 33.3 | 39.4 | 124.4 | 32.8 | -23.9 | -75.6 | 30.8 |
| |
| Free cash flow | 27.5 | 52.0 | 48.5 | 44.5 | 22.5 | 36.1 | 71.1 | 66.7 |
| Per share (diluted) | $0.27 | $0.52 | $0.51 | $0.50 | $0.25 | $0.42 | $0.91 | $1.01 |
| |
| Cash paid for interest | 22.5 | 27.5 | 26.1 | 27.5 | 36.5 | 30.1 | | |