Goodwill - Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Goodwill [Roll Forward] | ||
| Goodwill balance, beginning of year | $ 20,317 | $ 15,504 |
| Goodwill balance, end of year | 38,019 | 20,317 |
| Tictail, Inc. | ||
| Goodwill [Roll Forward] | ||
| Increase related to acquisitions | 15,125 | 0 |
| Solutions Alveo Inc. | ||
| Goodwill [Roll Forward] | ||
| Increase related to acquisitions | 2,577 | 0 |
| Oberlo UAB | ||
| Goodwill [Roll Forward] | ||
| Increase related to acquisitions | $ 0 | $ 4,813 |