Pension and Postretirement Benefits - Components of Net Periodic Benefit Cost of Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Domestic Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 8	$ 48	$ 56
Interest cost	198	197	585	604
Expected return on plan assets	(65)	(55)	(145)	(162)
Recognized net actuarial loss	124	106	370	336
Net periodic benefit cost	270	256	858	834
Domestic Plans | Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	22	60	69
Interest cost	129	92	337	311
Amortization of prior service credit	(51)	(107)	(154)	(323)
Recognized net actuarial loss	187	3	304	123
Net periodic benefit cost	269	10	547	180
Foreign Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	138	138	418	396
Interest cost	91	120	273	348
Expected return on plan assets	(126)	(156)	(382)	(450)
Recognized net actuarial loss	38	48	120	137
Net periodic benefit cost	$ 141	$ 150	$ 429	$ 431