| In millions, except per share items | Sep-30-18 | Jun-30-18 | Mar-31-18 | Dec-31-17 | Sep-30-17 | Jun-30-17 | Mar-31-17 | Dec-31-16 |
| | 10-Q | 10-Q | 10-Q | 8-K | 10-Q | 10-Q | 10-Q | 10-K |
| Revenue | 44.5 | 48.6 | 51.5 | 54.4 | 57.3 | 59.8 | 62.8 | 63.2 |
| Revenue growth | -22.3% | -18.7% | -17.9% | -14.0% | -8.4% | -3.1% | 3.4% | 1.1% |
| Cost of revenue and operating expenses: | | | | | | | | |
| Network access costs | 5.7 | | | | | | | |
| Network operations | 4.1 | 4.4 | 4.5 | | 4.8 | 5.0 | 5.3 | |
| Research and development | 5.7 | 5.9 | 6.0 | | 7.8 | 7.5 | 7.1 | 7.3 |
| Sales and marketing | 10.3 | 10.1 | 10.3 | 10.2 | 10.4 | 10.5 | 10.8 | 11.2 |
| General and administrative | 10.7 | 11.7 | 11.3 | 11.5 | 11.2 | 10.4 | 10.6 | 10.8 |
| Operating loss | -17.7 | -19.3 | -19.7 | -20.1 | -16.9 | -11.7 | -8.0 | -7.3 |
| Operating margin | -39.7% | -39.8% | -38.2% | -36.9% | -29.5% | -19.6% | -12.7% | -11.6% |
| |
| Other income (expense): | | | | | | | | |
| Interest income (expense), net | -0.5 | 0.1 | 0.1 | 0.1 | 0.0 | 0.1 | 0.0 | 0.0 |
| Foreign exchange gain (loss) | 0.6 | 0.6 | 0.3 | 0.4 | -0.3 | -0.2 | -0.2 | -0.2 |
| Change in fair value of derivative | -0.2 | | | | | | | |
| Total other income (expense) | -0.8 | | | -0.2 | -0.2 | | | |
| Loss before provision for income taxes | 1.9 | 0.8 | 0.3 | -20.4 | -17.2 | -11.8 | -8.1 | -7.5 |
| Provision for income taxes | 0.0 | 0.0 | 0.1 | 0.2 | 0.4 | 0.4 | 0.2 | 0.2 |
| Net loss | -18.5 | -19.5 | -20.3 | -20.6 | -17.6 | -12.2 | -8.4 | -7.8 |
| Comprehensive loss | -18.5 | -19.5 | -20.3 | -20.6 | -17.6 | -12.2 | -8.4 | -7.8 |
| |
| Total net income (loss) per share (in dollars per share) | ($0.89) | ($1.19) | ($1.21) | ($1.22) | ($1.18) | ($0.19) | ($0.13) | ($0.12) |
| |
| Weighted average shares outstanding - basic and diluted (in shares) | 54.5 | 54.2 | 52.0 | 51.0 | 50.5 | 65.0 | 64.5 | 63.9 |