Pension Plans and Other Postretirement Benefits Estimated Amounts to Be Amortized from Accumulated Other Comprehensive Income into Net Periodic Benefit Costs (Details) - Scenario, Forecast $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Future amortization of prior service benefit	$ 75
Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Future amortization of prior service benefit	36
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Future amortization of prior service benefit	$ (95)