| In millions, except per share items | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 13.1 | 85.8 | 12.2 | -17.8 | 19.2 | 51.2 | 107.4 | 60.8 |
| Depreciation and amortization | 10.6 | 9.4 | 8.9 | 12.5 | 14.6 | 15.7 | 11.7 | 13.5 |
| Stock-based compensation | 0.9 | 6.1 | 11.1 | 4.2 | 3.7 | 4.5 | 3.6 | 4.1 |
| Tax benefit from stock-based compensation | | -0.9 | 0.9 | | -0.2 | -0.3 | | 0.1 |
| Deferred taxes | | | | | -6.4 | -12.2 | 79.3 | -1.0 |
| Change in working capital [+] | 15.1 | -36.4 | 33.2 | 50.9 | -14.5 | -32.2 | -139.7 | -18.0 |
| Income taxes | 6.2 | 20.6 | -1.0 | 54.4 | -0.2 | 13.7 | -81.6 | -11.8 |
| Other | 8.9 | -57.0 | 34.2 | -3.5 | -14.3 | -45.9 | -58.1 | -6.2 |
| Other operating activities | 9.3 | -107.9 | -79.7 | 18.1 | 97.1 | 123.1 | 13.3 | 12.6 |
| Cash from operations | 49.0 | -43.9 | -13.4 | 67.9 | 113.5 | 149.8 | 75.6 | 72.1 |
| |
| Capital expenditures | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -0.1 | 0.0 | 0.2 |
| Purchases of property and equipment | | | | | | -0.1 | | 0.2 |
| Sales of short-term investments, net [+] | 303.5 | 458.0 | 175.2 | -66.8 | 228.6 | 174.0 | 227.8 | -38.8 |
| Purchases of short-term investments | -661.0 | -592.6 | -349.6 | -505.4 | -589.3 | -573.9 | -431.4 | -326.7 |
| Sales of short-term investments | 964.5 | 1,050.6 | 524.8 | 438.6 | 817.9 | 747.9 | 659.2 | 287.9 |
| Other cash from investing | -325.3 | -383.9 | -191.2 | 46.3 | -356.2 | -341.6 | -284.3 | 15.6 |
| Cash from investing | -21.8 | 74.1 | -16.0 | -20.5 | -127.6 | -167.7 | -56.5 | -23.0 |
| |
| Cash dividends paid | -17.5 | -17.4 | -17.1 | -16.9 | -16.6 | -16.5 | -16.5 | -16.1 |
| Issuance of common stock, net | 3.0 | 5.4 | 15.2 | 9.9 | 2.0 | 5.9 | 3.4 | 3.9 |
| Other cash from financing | | | -0.4 | | 21.7 | 0.3 | | -15.6 |
| Cash from financing | -14.5 | -12.0 | -2.3 | -7.0 | 7.1 | -10.3 | -13.1 | -27.8 |
| |
| Free cash flow | 49.0 | -43.9 | -13.4 | 67.9 | 113.5 | 149.7 | 75.6 | 72.3 |
| Per share (diluted) | $1.11 | ($1.00) | ($0.31) | $1.61 | $2.70 | $3.60 | $1.83 | $1.78 |
| |
| Cash paid for interest | 4.7 | 4.8 | 5.7 | 5.7 | 5.4 | 5.3 | 5.2 | 8.5 |