Pension Plans and Other Postretirement Benefits Estimated Amounts to Be Amortized from Accumulated Other Comprehensive Income into Net Periodic Benefit Costs (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	$ (48)
U.S. Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	60
Foreign Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	$ 40