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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Domestic Plans | Pension Plans
Net periodic benefit cost:
Service cost			$ 0
Interest cost	110	162	315	490
Expected return on plan assets	(20)	(74)	(35)	(109)
Amortization of prior service credit			0
Recognized net actuarial (gain) loss	157	130	467	395
Net periodic benefit cost	247	218	747	776
Domestic Plans | Postretirement Benefit Plans
Net periodic benefit cost:
Service cost	24	7	52	38
Interest cost	41	64	136	222
Expected return on plan assets			0
Amortization of prior service credit	(1)	(36)	(4)	(109)
Recognized net actuarial (gain) loss	(12)	(26)	86	13
Net periodic benefit cost	52	9	270	164
Foreign Pension Plans
Net periodic benefit cost:
Service cost	113	112	343	330
Interest cost	77	87	233	254
Expected return on plan assets	(127)	(134)	(382)	(394)
Amortization of prior service credit			0
Recognized net actuarial (gain) loss	49	48	148	138
Net periodic benefit cost	$ 112	$ 113	$ 342	$ 328