Stock incentive plans - Compensation expense (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2017 |
Mar. 31, 2016 |
|
| Recognized stock-based compensation expense | ||
| Total stock-based compensation expense | $ 3,044 | $ 3,605 |
| Stock-based compensation expense capitalized | 194 | 182 |
| Network operations | ||
| Recognized stock-based compensation expense | ||
| Total stock-based compensation expense | 546 | 646 |
| Development and technology | ||
| Recognized stock-based compensation expense | ||
| Total stock-based compensation expense | 270 | 312 |
| Selling and marketing | ||
| Recognized stock-based compensation expense | ||
| Total stock-based compensation expense | 426 | 549 |
| General and administrative | ||
| Recognized stock-based compensation expense | ||
| Total stock-based compensation expense | $ 1,802 | $ 2,098 |