| In millions, except per share items | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 28.0 | 27.0 | -12.1 | -83.0 | -1.3 | -18.7 | -37.1 | 0.0 |
| Depreciation and amortization [+] | 6.9 | 7.8 | 10.0 | 9.5 | 6.5 | 4.1 | 2.6 | 1.5 |
| Depreciation | 6.4 | 7.8 | 10.0 | 9.5 | 6.5 | 4.1 | 2.6 | 1.5 |
| Amortization of intangible assets | 0.5 | | | | | | | |
| Asset impairment charges | | 5.7 | | | | | | |
| Stock-based compensation | 11.0 | 11.8 | 12.5 | 15.9 | 11.6 | 2.8 | 0.4 | 0.2 |
| Change in working capital [+] | 7.4 | 7.2 | -7.2 | 9.5 | 16.2 | 7.3 | 3.4 | 2.4 |
| Accounts payable | 2.5 | 1.5 | -2.6 | 2.6 | 0.2 | 1.6 | -0.6 | 1.4 |
| Accrued expenses | 5.0 | 5.6 | -4.9 | 5.6 | 16.0 | 6.0 | 4.0 | |
| Other | -0.1 | 0.1 | 0.2 | 1.4 | -0.1 | -0.3 | -0.1 | 1.0 |
| Other operating activities | 229.1 | 206.2 | 208.4 | 182.3 | 85.9 | 107.7 | 62.0 | 6.1 |
| Cash from operations | 282.4 | 265.8 | 211.6 | 134.3 | 118.9 | 103.2 | 31.4 | 10.3 |
| |
| Capital expenditures [+] | -12.5 | -6.4 | -4.3 | -11.3 | -17.9 | -11.0 | -5.8 | -1.8 |
| Purchases of property and equipment | -3.2 | -1.1 | -1.3 | -6.6 | -13.7 | -7.6 | -3.7 | -1.8 |
| Capitalized product costs | -9.3 | -5.4 | -2.9 | -4.6 | -4.2 | -3.5 | -2.1 | |
| Other cash from investing | -291.2 | -395.3 | -154.6 | -572.0 | -150.5 | -360.5 | -170.9 | -65.9 |
| Cash from investing | -303.6 | -401.7 | -158.9 | -583.3 | -168.4 | -371.6 | -176.7 | -67.7 |
| |
| Issuance of common stock, net | -44.0 | | | -0.9 | | 213.8 | | |
| Option exercises | 2.3 | 1.5 | 2.3 | 2.8 | 2.1 | 4.6 | 0.4 | |
| Financing costs | -5.3 | -6.0 | -4.1 | -6.3 | -1.7 | -5.7 | -2.1 | |
| Other cash from financing | 61.9 | 117.2 | -64.3 | 372.1 | -10.1 | 269.2 | 140.9 | 0.0 |
| Cash from financing | 20.9 | 121.7 | -62.5 | 374.7 | -10.5 | 484.1 | 142.6 | 0.0 |
| |
| Free cash flow | 279.2 | 264.8 | 210.2 | 127.6 | 105.3 | 95.6 | 27.7 | 8.4 |
| Per share (diluted) | $3.51 | $3.30 | $2.84 | $1.73 | $1.45 | $1.75 | $5.96 | $1,770.99 |
| |
| Cash paid for interest | 40.0 | 42.2 | 41.9 | 24.8 | 15.4 | 15.0 | 10.6 | |
| Cash paid for income taxes | 9.3 | | | | | | | |