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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
UNITED STATES | Pension Plans
Net periodic benefit cost:
Service cost		$ 15		$ 46
Interest cost	$ 162	209	$ 490	646
Expected return on plan assets	(74)	(35)	(109)	(74)
Recognized net actuarial loss	130	96	395	302
Net periodic benefit cost	218	285	776	920
UNITED STATES | Postretirement Benefit Plans
Net periodic benefit cost:
Service cost	7	13	38	48
Interest cost	64	93	222	343
Amortization of prior service credit	(36)	(47)	(109)	(141)
Recognized net actuarial loss	(26)	(43)	13	84
Net periodic benefit cost	9	16	164	334
Foreign Pension Plans
Net periodic benefit cost:
Service cost	112	101	330	303
Interest cost	87	92	254	281
Expected return on plan assets	(134)	(122)	(394)	(364)
Recognized net actuarial loss	48	37	138	111
Net periodic benefit cost	$ 113	$ 108	$ 328	$ 331