Pension and Postretirement Benefits - Components of Net Periodic Benefit Cost of Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Domestic Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 9
Interest cost	187	229
Expected return on plan assets	(35)	(39)
Recognized net actuarial loss	122	136
Net periodic benefit cost	276	335
Domestic Plans | Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	24	30
Interest cost	94	126
Amortization of prior service credit	(84)	(111)
Recognized net actuarial loss	52	100
Net periodic benefit cost	86	145
Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	142	130
Interest cost	92	114
Expected return on plan assets	(129)	(148)
Recognized net actuarial loss	41	45
Net periodic benefit cost	$ 146	$ 141