Benefit Plan (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Benefit Plan | |||
| Voluntary employer matching contributions | $ 4,038 | $ 2,270 | $ 1,521 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. No definition available.
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