Pension and Other Postretirement Benefits (Details 6) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	[1]	$ (10,726)	$ 8,867	$ (9,586)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost		(800)
Net loss		7,787
Amortization of prior service costs (credits)		117
Amortization of actuarial loss		7,140
Foreign exchange rate changes		(1,262)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		12,982
Other postretirement benefit plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost		0
Net loss		(2,392)
Amortization of prior service costs (credits)		(43)
Amortization of actuarial loss		170
Foreign exchange rate changes		9
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		$ (2,256)

[1] Net of tax of $4,469, $(4,687) and $3,916 for the years ended December 31, 2017, 2016 and 2015, respectively.