Employee Benefit Plan (Details) - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Retirement Benefits [Abstract] | |||
Eligible employees maximum contribution percentage | 60.00% | ||
Contributions by employer | $ 20.2 | $ 15.7 | $ 11.2 |