Pensions and Other Postretirement Benefit Plans (Schedule of Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning of year	$ 180,672	$ 171,387
Actual return on plan assets, net of expenses	19,182	19,740
Employer contributions	4,645	6,605
Plan participants' contributions	211	249
Benefits paid	(7,697)	(7,057)
Settlements	(8)	(2,308)
Foreign currency changes	8,581	(7,944)
Fair value of plan assets, end of year	205,586	180,672
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning of year
Actual return on plan assets, net of expenses
Employer contributions	4,230	4,812
Plan participants' contributions		72
Benefits paid	(4,230)	(4,884)
Settlements
Foreign currency changes
Fair value of plan assets, end of year