Retirement Plan (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Retirement Plan | |||
| Eligible Employees to contribute | 100.00% | ||
| Employee contribution | 33.00% | ||
| Maximum matching contributions as a percentage of eligible compensation | 6.00% | ||
| Contributions made by Company | $ 1.3 | $ 1.1 | $ 0.8 |