| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 387.9 | -133.5 | -5.5 | -0.8 | -88.9 | -106.1 | -18.2 | 173.2 |
| Depreciation and amortization [+] | 111.2 | 89.1 | 74.3 | 75.7 | 72.4 | 78.9 | 79.9 | 81.7 |
| Depreciation | 110.4 | 86.7 | 74.3 | 75.7 | 72.4 | 78.9 | 79.9 | 81.7 |
| Amortization of intangible assets | 0.8 | 2.4 | | | | | | |
| Asset impairment charges | 1.7 | 3.5 | 103.0 | | 19.0 | 88.4 | 79.2 | |
| Stock-based compensation | 6.7 | 10.5 | 5.6 | 4.3 | 3.2 | 3.8 | 2.8 | 2.8 |
| Change in working capital [+] | -145.2 | -2.5 | 28.8 | 20.9 | -37.0 | -0.6 | 7.4 | 16.4 |
| Accounts receivable | -182.7 | -16.5 | 40.5 | 10.8 | -36.4 | 8.7 | 8.0 | 13.4 |
| Deferred revenues | 2.6 | -1.6 | 3.0 | 0.0 | -0.9 | -4.7 | 4.4 | |
| Other | 34.9 | 15.6 | -14.6 | 10.2 | 0.3 | -4.6 | -5.1 | 3.0 |
| Other operating activities | -74.6 | -43.3 | 9.8 | -12.6 | 18.9 | -46.9 | -22.2 | -51.3 |
| Cash from operations | 287.8 | -76.2 | 216.1 | 87.5 | -12.5 | 17.4 | 129.0 | 222.7 |
| |
| Capital expenditures [+] | -0.7 | -1.0 | -0.5 | -0.6 | -1.1 | -0.4 | -2.9 | -1.0 |
| Purchases of property and equipment | -0.7 | -1.0 | -0.5 | -0.6 | -1.1 | -0.4 | -2.9 | -1.0 |
| Sales of property and equipment | 116.0 | 78.0 | 50.0 | 36.6 | 148.9 | 173.5 | 2.0 | 17.1 |
| Purchases of short-term investments, net | -80.0 | | | | | | | |
| Purchases of short-term investments | -105.0 | | | | | | | |
| Sales of short-term investments | 25.0 | | | | | | | |
| Other cash from investing | 7.5 | 56.2 | -17.2 | 71.8 | -24.1 | -309.9 | 3.4 | 98.1 |
| Cash from investing | 42.8 | 133.3 | 32.4 | 107.9 | 123.7 | -136.8 | 2.5 | 114.2 |
| |
| Cash dividends paid | -69.8 | -40.9 | -6.8 | | | | -202.0 | -200.0 |
| Repurchase of common stock, net | -20.0 | -16.7 | -30.0 | | | | | |
| Other cash from financing | -95.9 | -116.2 | -146.3 | -162.8 | -64.2 | 98.0 | -155.3 | -6.3 |
| Cash from financing | -185.8 | -173.8 | -183.1 | -162.8 | -64.2 | 98.0 | -357.3 | -206.3 |
| |
| Free cash flow | 287.1 | -77.2 | 215.6 | 86.9 | -13.6 | 17.0 | 126.1 | 221.8 |
| Per share (diluted) | $5.76 | ($2.01) | $7.60 | $2.97 | ($0.47) | $0.58 | $4.32 | $7.61 |