Goodwill and Intangible Assets (Amortization expense) (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Amortization expense | |||
| Amortization of intangible assets | $ 5,212 | $ 4,598 | $ 1,474 |
| Cost of revenue | |||
| Amortization expense | |||
| Amortization of intangible assets | 3,164 | 3,052 | |
| Research and development | |||
| Amortization expense | |||
| Amortization of intangible assets | 193 | 188 | |
| Sales and marketing | |||
| Amortization expense | |||
| Amortization of intangible assets | $ 1,855 | $ 1,358 | |