Pensions and Other Postretirement Benefit Plans (Schedule of Amounts That Will Be Amortized from Accumulated Other Comprehensive Income) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	$ 2,232
Prior service cost/(benefit)	35
Total	2,267
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	2,956
Prior service cost/(benefit)	(4,488)
Total	$ (1,532)