Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Eligibility age, minimum	18 years
Employer's matching of employee contribution (in hundredths)	50.00%
Employee contribution matched (in hundredths)	6.00%
Employment term eligibility, minimum	3 months
Employee contribution vesting period	5 years
Previously forfeited matching contributions used to fund current matching contributions	$ 69	$ 198	$ 17
401 (k) expense	$ 805	$ 882	$ 817