Employee Retirement Plans (Components of Net Periodic Pension and Other Post-Retirement Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 46	$ 59	$ 66
Amortization of unrecognized prior service cost	2	6	14
Gain amortization	19	13	0
Net periodic pension cost	$ 29	$ 52	$ 80
Discount rate	3.55%	3.81%	3.94%