Pension Plan (Details) - Components of net periodic pension cost - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Components of net periodic pension cost [Abstract]
Interest cost	$ 114	$ 117	$ 227	$ 233
Expected return on plan assets	(203)	(180)	(406)	(359)
Amortization of net actuarial loss	56	55	112	109
Net periodic pension benefit	$ (33)	$ (8)	$ (67)	$ (17)