Segment and Geographical Information - Segment Reporting Information by Segment (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||||
|---|---|---|---|---|---|---|
Jun. 30, 2018 |
Jul. 01, 2017 |
Jun. 30, 2018 |
Jul. 01, 2017 |
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| Segment Reporting Information [Line Items] | ||||||
| Revenue | [1] | $ 45,966 | $ 41,972 | $ 93,291 | $ 85,338 | |
| United States | ||||||
| Segment Reporting Information [Line Items] | ||||||
| Revenue | 41,363 | 38,336 | 83,900 | 78,178 | ||
| Non-US | ||||||
| Segment Reporting Information [Line Items] | ||||||
| Revenue | $ 4,603 | $ 3,636 | $ 9,391 | $ 7,160 | ||
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