Defined Contribution Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan (Textual)
Percentage of employees salary matches participant contributions	100.00%
Percentage of maximum employees salary	5.00%
Costs recognized related to employer	$ 1,298	$ 941	$ 335