Pension and Postretirement Benefits - Components of Net Periodic Benefit Cost of Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
UNITED STATES | Pension Plans
Net periodic benefit cost:
Service cost		$ 16		$ 31
Interest cost	$ 168	223	$ 328	437
Expected return on plan assets	(34)	(5)	(35)	(39)
Recognized net actuarial loss	130	100	265	206
Net periodic benefit cost	264	334	558	635
UNITED STATES | Postretirement Benefit Plans
Net periodic benefit cost:
Service cost	16	15	31	35
Interest cost	70	126	158	250
Amortization of prior service credit	(37)	(47)	(73)	(94)
Recognized net actuarial loss	(43)	50	39	127
Net periodic benefit cost	6	144	155	318
Foreign Pension Plans
Net periodic benefit cost:
Service cost	108	101	218	202
Interest cost	83	93	167	188
Expected return on plan assets	(129)	(121)	(260)	(243)
Recognized net actuarial loss	44	37	90	73
Net periodic benefit cost	$ 106	$ 110	$ 215	$ 220