Employee Benefit Plan - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit Plan [Abstract]
Defined Contribution Plan, Employer Matching Contribution, Percent	100.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	5.00%
Defined Contribution Plan, Cost	$ 604	$ 444	$ 365