Employee Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Benefit Plan
Minimum age required to be eligible for contribution under the Retirement Plan	21 years
Employer matching contribution (as a percent)	100.00%
Maximum amount contributed by employee from employees base salary (as a percent)	8.00%
Compensation expense	$ 3,018	$ 3,019	$ 2,775