Stock incentive plans - Compensation expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | $ 3,155 | $ 3,684 | $ 9,227 | $ 11,016 |
| Stock-based compensation expense capitalized | 208 | 163 | 600 | 530 |
| Network operations | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 549 | 552 | 1,602 | 1,660 |
| Development and technology | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 323 | 275 | 915 | 825 |
| Selling and marketing | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | 511 | 524 | 1,377 | 1,589 |
| General and administrative | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation expense | $ 1,772 | $ 2,333 | $ 5,333 | $ 6,942 |