| 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 | 9.3 | 10.5 | 11.4 | 13.2 | 13.4 | 13.5 | 14.3 | 16.1 |
| Revenue growth | -30.8% | -21.8% | -20.0% | -17.8% | -15.6% | -18.3% | -3.0% | 4.5% |
| Cost of revenue and operating expenses: | | | | | | | | |
| Network access costs | 5.7 | | | | 10.3 | | | |
| Network operations | 1.3 | 1.4 | 1.4 | | 1.6 | 1.5 | 1.7 | |
| Research and development | 1.8 | 2.0 | 2.0 | | 1.9 | 2.1 | 2.0 | 1.7 |
| Sales and marketing | 2.8 | 2.4 | 2.5 | 2.7 | 2.5 | 2.6 | 2.5 | 2.8 |
| General and administrative | 2.4 | 3.0 | 2.6 | 2.7 | 3.4 | 2.5 | 2.8 | 2.5 |
| Total cost of revenue and operating expenses | 14.0 | 15.1 | 15.2 | | 19.8 | 18.4 | 18.5 | |
| Operating loss | -4.8 | -4.6 | -3.8 | -4.5 | -6.4 | -4.9 | -4.2 | -1.4 |
| Operating margin | -51.2% | -43.4% | -33.4% | -34.2% | -48.0% | -36.6% | -29.2% | -8.5% |
| |
| Other income (expense): | | | | | | | | |
| Interest income (expense), net | -0.6 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Foreign exchange gain (loss) | -0.1 | 0.2 | -0.1 | 0.7 | -0.2 | -0.1 | 0.0 | 0.0 |
| Change in fair value of derivative | -0.2 | | | | | | | |
| Total other income (expense) | -0.8 | | | 0.0 | -0.2 | | | |
| Loss before provision for income taxes | -5.6 | -4.5 | -3.9 | 15.9 | -6.6 | -5.1 | -4.2 | -1.3 |
| Provision for income taxes | 0.0 | 0.1 | 0.1 | -0.2 | 0.1 | 0.2 | 0.1 | 0.0 |
| Tax rate | | | | | | | | |
| Net loss | -5.6 | -4.5 | -4.0 | -4.3 | -6.7 | -5.3 | -4.3 | -1.3 |
| Comprehensive loss | -5.6 | -4.5 | -4.0 | -4.3 | -6.7 | -5.3 | -4.3 | -1.3 |
| |
| Total net income (loss) per share (in dollars per share) | ($0.71) | ($0.06) | ($0.06) | ($0.06) | ($1.01) | ($0.08) | ($0.07) | ($0.02) |
| |
| Weighted average shares outstanding - basic and diluted (in shares) | 7.9 | 74.2 | 69.9 | 66.1 | 6.6 | 65.7 | 65.6 | 64.3 |