Stock incentive plans - Compensation expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | $ 2,946 | $ 4,288 | $ 6,072 | $ 7,332 |
| Stock-based compensation expense capitalized | 206 | 173 | 392 | 367 |
| Network operations | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 516 | 562 | 1,053 | 1,108 |
| Development and technology | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 314 | 280 | 592 | 550 |
| Selling and marketing | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 393 | 639 | 866 | 1,065 |
| General and administrative | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | $ 1,723 | $ 2,807 | $ 3,561 | $ 4,609 |