| 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 | -155.9 | -18.6 | 78.5 | 99.0 | 49.6 | 38.1 | 23.9 | 5.7 |
| Depreciation and amortization [+] | 42.4 | 30.2 | 21.6 | 11.8 | 8.9 | 28.0 | 22.7 | 13.5 |
| Depreciation | 42.4 | 30.2 | 21.6 | 11.8 | 8.9 | 5.1 | 5.0 | 4.0 |
| Amortization of intangible assets | | | | | | 22.9 | 17.7 | 9.5 |
| Stock-based compensation | 84.5 | 72.9 | 55.3 | 32.7 | 23.6 | 13.5 | 9.4 | 4.9 |
| Deferred taxes | -9.5 | -7.7 | 1.7 | -31.2 | 1.0 | -3.8 | 4.6 | 1.7 |
| Change in working capital [+] | 111.6 | 11.8 | -1.2 | -0.7 | -12.3 | -32.4 | 11.4 | 13.1 |
| Accounts receivable | 6.9 | -11.6 | -6.1 | -26.2 | -12.0 | -4.3 | -7.4 | -8.3 |
| Other current assets | -22.6 | -13.9 | -16.3 | 5.5 | -8.7 | 0.2 | -1.7 | -2.4 |
| Accounts payable | -2.0 | 2.0 | 11.2 | -4.2 | -3.2 | 3.3 | -0.3 | 2.1 |
| Other | 129.3 | 35.3 | 10.0 | 24.3 | 11.6 | -31.6 | 20.7 | 21.8 |
| Other operating activities | 61.9 | 94.0 | 69.6 | 42.5 | 27.0 | 1.4 | 0.9 | 1.9 |
| Cash from operations | 135.0 | 182.6 | 225.5 | 154.1 | 97.8 | 44.8 | 72.9 | 40.8 |
| |
| Capital expenditures [+] | -120.2 | -103.7 | -74.2 | -40.3 | -36.9 | -11.3 | -7.1 | -7.0 |
| Purchases of property and equipment | -63.0 | -55.2 | -43.0 | -19.0 | -24.1 | -4.2 | -3.7 | -4.4 |
| Capitalized product costs | -57.2 | -48.5 | -31.2 | -21.3 | -12.8 | -7.1 | -3.4 | -2.6 |
| Acquisitions | -0.5 | 0.1 | -517.9 | -333.3 | -65.8 | -73.9 | | |
| Sales of short-term investments | | | | | | 189.9 | 1.5 | |
| Sales of short-term investments | | | | | | 189.9 | 1.5 | |
| Other cash from investing | -4.1 | -44.9 | -1.9 | 36.6 | 57.2 | -221.1 | -113.2 | 13.3 |
| Cash from investing | -124.7 | -148.4 | -594.0 | -337.0 | -45.5 | -116.4 | -118.7 | 6.2 |
| |
| Issuance of common stock, net | | | 200.0 | | -14.8 | | 142.4 | -1.4 |
| Option exercises | 9.6 | 4.5 | 14.2 | 16.4 | 13.5 | 11.9 | 8.3 | 1.4 |
| Financing costs | -0.1 | -9.1 | | -2.0 | -1.5 | | | |
| Other cash from financing | -17.8 | 124.6 | 160.9 | 192.5 | 46.1 | 51.3 | 27.2 | 0.9 |
| Cash from financing | -27.3 | 129.3 | 346.7 | 178.1 | 19.3 | 39.4 | 161.3 | -1.8 |
| |
| Free cash flow | 72.0 | 127.5 | 182.5 | 135.2 | 73.7 | 40.6 | 69.3 | 36.4 |
| Per share (diluted) | $0.16 | $0.87 | $1.64 | $1.29 | $0.71 | $0.39 | $0.81 | $0.60 |