Employee Benefit Plans Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax
Unrecognized prior service cost	$ 50	$ 60
Unrecognized net loss/(gain)	15,600	17,910
Total accumulated other comprehensive income (loss) recognized at December 31	$ 15,650	$ 17,970