Pension Plans and Other Postretirement Benefits - Domestic and Foreign Pension and Postretirement Defined Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total net pension and postretirement benefits credit	$ (890)	$ (26)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,268	1,003
Interest cost	8,027	8,288
Expected return on assets	(10,764)	(9,908)
Amortization of prior service benefit	22	27
Total net pension and postretirement benefits credit	(1,447)	(590)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	29	31
Interest cost	542	585
Expected return on assets	(2)	(28)
Amortization of prior service benefit	(12)	(24)
Total net pension and postretirement benefits credit	$ 557	$ 564