Employee Benefit Plans - Benefit Obligations of Defined Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year			$ 1,187	$ 1,023
Service cost	$ 94	$ 35	206	51
Interest cost	18	11	31	21
Benefit obligation, end of year	$ 1,424	$ 1,095	$ 1,424	$ 1,095