Other Postretirement Benefits (Amounts Recognized in the Consolidated Financial Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued post retirement liability: Current portion	$ 327	$ 360
Accrued post retirement liability: Long term portion	743	1,016
Net amount recognized	1,241	1,573
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued post retirement liability: Current portion	314	294
Accrued post retirement liability: Long term portion	6,706	6,908
Pre-tax accumulated other comprehensive loss – unamortized post-retirement healthcare costs	2,809	3,150
Net amount recognized	$ 4,211	$ 4,052