| In millions, except per share items | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 | Dec-31-09 | Dec-31-08 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | S-1/A | S-1 |
| Revenue | 296.2 | 259.2 | 177.7 | 103.7 | 47.8 | 16.7 | 6.3 |
| Revenue growth | 14.3% | 45.9% | 71.4% | 116.8% | 187.2% | 165.1% | |
| Cost of revenue | 179.8 | 154.8 | 105.7 | 63.6 | 31.6 | 11.6 | |
| Gross profit | 116.4 | 104.4 | 71.9 | 40.1 | 16.2 | 4.6 | |
| Gross margin | 39.3% | 40.3% | 40.5% | 38.7% | 33.9% | 27.8% | |
| |
| Operating expenses: | | | | | | | |
| Sales and marketing | 53.6 | 38.7 | 23.8 | 14.3 | 8.5 | 4.6 | |
| Technology and development | 29.5 | 19.0 | 13.6 | 5.2 | 2.2 | 1.1 | |
| General and administrative | 88.6 | 61.9 | 39.0 | 21.3 | 12.5 | 6.3 | |
| Total operating expenses | 265.2 | 119.5 | 76.4 | 81.6 | 23.2 | 12.0 | |
| Loss from operations | -148.8 | -15.1 | -4.5 | -0.7 | -7.0 | -7.4 | |
| Operating margin | -50.2% | -5.8% | -2.5% | -0.7% | -14.6% | -44.5% | |
| |
| Other expense | | | | | | | |
| Interest expense, net | -0.1 | -0.1 | -0.1 | 0.0 | 0.0 | 0.1 | |
| Total other expense | -0.1 | 0.1 | -0.9 | -0.1 | -0.1 | -0.1 | |
| Loss before income taxes | -148.9 | -15.2 | -5.4 | -0.8 | -7.1 | -7.6 | |
| Income tax expense | 0.2 | 0.0 | 0.1 | -0.5 | | | |
| Net loss | -149.1 | -15.1 | -5.4 | -0.3 | -7.1 | -7.6 | |
| |
| Net loss attributable to common stockholders | | | | | | | |
| Net loss per share: | | | | | | | |
| Basic and diluted (in dollars per share) | ($1.36) | ($0.18) | ($0.11) | ($0.32) | ($0.56) | ($0.56) | |
| |
| Weighted average common shares outstanding: | | | | | | | |
| Basic and diluted (in shares) | 109.6 | 84.0 | 61.0 | 16.4 | 18.0 | 16.8 | |
| |
| Stock-based compensation expense included above: | | | | | | | |
| Stock-based compensation expense | 13.6 | 9.0 | 7.5 | 1.8 | 0.4 | 0.2 | |