| In millions, except per share items | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 |
| | 10-K | 10-K | 10-K | 10-K | 10-K/A | 10-K | 10-K | 10-K |
| Net income | -37.7 | 6.7 | 12.8 | 13.6 | 9.5 | 13.3 | 9.3 | 6.2 |
| Depreciation and amortization [+] | 19.7 | 15.2 | 13.2 | 11.4 | 9.7 | 7.6 | 7.5 | 7.1 |
| Depreciation | 18.8 | 14.3 | 12.0 | 9.9 | | | | |
| Amortization | 0.9 | 0.9 | 1.2 | 1.5 | | | | |
| Stock-based compensation | 0.3 | 0.4 | 0.6 | 1.0 | 1.9 | 0.3 | 0.3 | 0.3 |
| Tax benefit from stock-based compensation | | | 0.2 | 0.0 | 0.0 | | | |
| Deferred taxes | -3.6 | -15.7 | 7.6 | 4.2 | -2.5 | -0.1 | 0.6 | 2.4 |
| Change in working capital [+] | 6.4 | 6.9 | -7.8 | -9.5 | 5.1 | -0.2 | -0.7 | -0.3 |
| Accounts receivable | | | | | -2.6 | -1.2 | 1.6 | -0.8 |
| Inventories | -0.6 | -2.1 | -4.9 | -3.9 | 1.3 | -0.6 | -2.5 | -0.2 |
| Other current assets | 0.4 | 0.2 | 2.2 | -1.0 | | 0.0 | 0.3 | -0.3 |
| Accounts payable | | | | | 7.7 | | 0.2 | -1.7 |
| Accrued expenses | 8.0 | 0.7 | -2.2 | 0.1 | -0.3 | 1.2 | 0.2 | 0.3 |
| Other | -1.4 | 8.2 | -2.9 | -4.8 | -1.1 | 0.4 | -0.4 | 2.4 |
| Other operating activities | -2.6 | 0.0 | 1.3 | -1.9 | -3.6 | -0.1 | 0.3 | 0.0 |
| Cash from operations | -17.5 | 13.4 | 27.8 | 18.8 | 20.2 | 20.8 | 17.5 | 15.7 |
| |
| Capital expenditures [+] | -3.4 | -49.2 | -88.9 | -63.2 | -25.8 | -12.2 | -6.8 | -5.5 |
| Purchases of property and equipment | -3.4 | -49.2 | -88.9 | -63.2 | -25.8 | -12.2 | -6.8 | -5.5 |
| Sales of property and equipment | 0.0 | | 0.0 | | | | | |
| Sales of short-term investments, net [+] | | | | | 5.0 | 0.0 | -3.0 | 7.5 |
| Purchases of short-term investments | | | | | 0.0 | 0.0 | -3.0 | |
| Sales of short-term investments | | | | | 5.0 | | | 7.5 |
| Other cash from investing | 2.2 | 0.1 | 0.4 | -12.0 | -16.7 | | | |
| Cash from investing | -1.2 | -49.1 | -88.4 | -75.2 | -37.4 | -12.2 | -9.8 | 2.0 |
| |
| Cash dividends paid | | -3.6 | -14.4 | -13.8 | -11.8 | -10.7 | -6.4 | -3.8 |
| Issuance of common stock, net | | 0.0 | | 32.1 | | | | |
| Option exercises | | 0.1 | 0.3 | 0.2 | 0.1 | 3.3 | 1.0 | 0.3 |
| Financing costs | -1.5 | -1.1 | -0.1 | -1.3 | | | | -0.1 |
| Other cash from financing | 18.4 | 32.2 | 68.8 | 40.3 | 23.0 | 6.9 | 1.2 | -9.5 |
| Cash from financing | 19.8 | 29.5 | 54.2 | 59.7 | 11.1 | -7.1 | -6.2 | -13.5 |
| |
| Free cash flow | -20.9 | -35.7 | -61.0 | -44.4 | -5.6 | 8.6 | 10.7 | 10.1 |
| Per share (diluted) | ($1.95) | ($3.43) | ($5.90) | ($4.51) | ($0.66) | $1.09 | $1.36 | $1.31 |
| |
| Cash paid for interest | 10.7 | 7.9 | 2.9 | 0.7 | | 0.4 | 0.4 | 0.6 |
| Cash paid for income taxes | -0.3 | -8.2 | 0.0 | 6.7 | | 2.8 | 3.4 | -2.4 |