Employee Benefits - Components of Net Periodic Cost Related to Other Post-Retirement Benefits (Details) - Other Postretirement Benefits Plan - U.S Plans - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 90	$ 155
Interest cost	240	335
Amortization of prior service cost	(437)	188
Amortization of net actuarial loss	175	0
Net periodic benefit cost	$ 68	$ 678