Stock incentive plans - Compensation expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation | $ 3,684 | $ 3,006 | $ 11,016 | $ 9,690 |
| Stock-based compensation expense capitalized | 163 | 182 | 530 | 553 |
| Network operations | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation | 552 | 483 | 1,660 | 1,660 |
| Development and technology | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation | 275 | 267 | 825 | 830 |
| Selling and marketing | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation | 524 | 424 | 1,589 | 1,431 |
| General and administrative | ||||
| Recognized stock-based compensation expense | ||||
| Total stock-based compensation | $ 2,333 | $ 1,832 | $ 6,942 | $ 5,769 |