Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 65	$ 338	$ 130	$ 676
Interest cost	151	117	302	234
Net periodic benefit cost	$ 216	$ 455	$ 432	$ 910