| In millions, except per share items | Dec-31-16 | Dec-26-15 | Dec-27-14 | Dec-28-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 | Dec-31-09 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | S-1/A | S-1 |
| Net income | 49.4 | 6.2 | -40.8 | -9.5 | 3.6 | 10.1 | 3.5 | 13.1 |
| Depreciation and amortization | 6.8 | 6.5 | 6.0 | 2.9 | 1.4 | 0.7 | 0.3 | 0.1 |
| Stock-based compensation | 38.8 | 29.8 | 24.7 | 32.5 | 3.6 | 0.0 | 0.0 | 0.1 |
| Tax benefit from stock-based compensation | -12.1 | -4.7 | | | | | | |
| Deferred taxes | -33.0 | 0.2 | 20.8 | -20.9 | | | | |
| Change in working capital [+] | -13.6 | 23.5 | -3.1 | 17.5 | 12.7 | 0.7 | 0.8 | -2.7 |
| Accounts receivable | -28.0 | -19.4 | -4.2 | -3.9 | -4.3 | -9.0 | -1.3 | -2.9 |
| Inventories | -9.9 | -0.2 | -8.8 | 1.4 | 2.1 | -4.8 | -3.3 | -1.4 |
| Other current assets | -2.5 | -2.6 | -0.9 | -3.3 | 1.6 | -3.9 | -0.2 | |
| Accounts payable | 1.3 | 1.3 | 1.0 | -1.8 | 0.4 | 2.0 | 0.5 | -0.1 |
| Accrued expenses | 9.9 | 17.8 | 1.7 | 8.3 | 4.0 | 5.5 | 1.4 | |
| Deferred revenues | 15.7 | 26.6 | 8.0 | 16.7 | 8.9 | 10.8 | 3.7 | |
| Other | | | | | | | | 1.8 |
| Cash from operations | 37.0 | 63.4 | 11.1 | 23.3 | 27.7 | 21.6 | 7.7 | 11.9 |
| |
| Capital expenditures | -8.1 | -6.3 | -7.6 | -4.0 | -2.0 | -2.1 | -0.8 | -0.4 |
| Purchases of property and equipment | -8.1 | -6.3 | -7.6 | -4.0 | -2.0 | -2.1 | -0.8 | -0.4 |
| Purchases of short-term investments, net | -19.2 | 20.1 | -52.1 | -57.7 | | | | |
| Purchases of short-term investments | -134.8 | -61.7 | -87.7 | -59.7 | | | | |
| Sales of short-term investments | 115.6 | 81.8 | 35.6 | 2.0 | | | | |
| Cash from investing | -27.3 | 13.8 | -59.7 | -61.8 | -2.0 | -2.1 | -0.8 | -0.4 |
| |
| Cash dividends paid | | | -0.5 | -7.0 | -18.2 | -12.2 | -13.9 | |
| Repurchase of common stock, net | | | | | | | -12.5 | |
| Option exercises | 11.7 | 9.5 | 11.2 | 1.7 | | | | |
| Other cash from financing | 30.6 | 13.5 | 19.4 | 108.4 | -1.9 | | 22.2 | -11.0 |
| Cash from financing | 18.9 | 4.0 | 7.6 | 99.7 | -20.1 | -12.2 | -4.2 | -11.0 |
| |
| Free cash flow | 29.0 | 57.1 | 3.5 | 19.3 | 25.7 | 19.5 | 6.8 | 11.5 |
| Per share (diluted) | $0.77 | $1.59 | $0.11 | $0.78 | $1.48 | $1.13 | $0.38 | |
| |
| Cash paid for income taxes | 2.8 | 0.7 | 0.5 | 0.2 | 0.1 | 0.1 | 0.0 | |