| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-05-18 | Dec-31-17 | Dec-31-16 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 8-K | 10-K | 10-K |
| Net income | 29.3 | -24.4 | 443.3 | 484.7 | 264.8 | 272.9 | 21.7 | 205.3 |
| Depreciation and amortization [+] | 15.2 | 15.2 | 16.2 | 23.9 | 42.6 | | 82.2 | 123.8 |
| Depreciation | 15.2 | 15.2 | 16.2 | 23.8 | 40.4 | 49.0 | 73.2 | 102.7 |
| Amortization of intangible assets | | | | 0.2 | 2.2 | | 9.0 | 21.1 |
| Stock-based compensation | 11.9 | 15.4 | 13.2 | 14.4 | 19.7 | | 21.4 | 18.5 |
| Change in working capital | 4.1 | -0.8 | -3.0 | -8.3 | -9.3 | | -27.4 | -16.1 |
| Other | 4.1 | -0.8 | -3.0 | -8.3 | -9.3 | | -27.4 | -16.1 |
| Other operating activities | 4.5 | 10.6 | -436.4 | -415.8 | -228.2 | | 2.1 | -167.8 |
| Cash from operations | 65.0 | 16.1 | 33.3 | 98.9 | 89.5 | | 100.0 | 163.7 |
| |
| Capital expenditures [+] | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | | 0.0 | 0.0 |
| Sales of property and equipment | 0.1 | | 655.3 | 771.8 | 961.1 | | 802.3 | 1,149.5 |
| Purchases of short-term investments, net | | | | 250.0 | 23.9 | | -276.2 | |
| Purchases of short-term investments | | | | | | | -276.2 | |
| Sales of short-term investments | | | | 250.0 | 23.9 | | | |
| Other cash from investing | -3.6 | -6.8 | -12.0 | -26.1 | -42.9 | | -60.5 | -123.8 |
| Cash from investing | -3.5 | -6.8 | 643.3 | 995.7 | 942.1 | | 465.6 | 1,025.7 |
| |
| Cash dividends paid | -112.2 | -6.0 | -427.8 | -428.6 | -304.6 | | | |
| Repurchase of common stock, net | -159.9 | -181.5 | -26.9 | -5.5 | -94.0 | | -3.2 | -70.0 |
| Financing costs | | | | | | | | -0.1 |
| Other cash from financing | -8.3 | -8.0 | -35.3 | -264.0 | -589.6 | | -303.0 | -853.2 |
| Cash from financing | -280.3 | -195.5 | -490.0 | -698.1 | -988.1 | | -306.2 | -923.2 |
| |
| Free cash flow | 65.0 | 16.1 | 33.3 | 98.9 | 89.5 | | 100.0 | 163.7 |
| Per share (diluted) | $0.58 | $0.13 | $0.26 | $0.78 | $0.73 | | $0.80 | $1.29 |