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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, 2021
Mar. 31, 2020
Domestic Plans | Pension Plans    
Net periodic benefit cost:    
Interest cost $ 114 $ 160
Expected return on plan assets (27) (1)
Recognized net actuarial loss 151 135
Net periodic benefit cost 238 294
Domestic Plans | Postretirement Benefit Plans    
Net periodic benefit cost:    
Service cost 13 15
Interest cost 55 88
Amortization of prior service credit (1) (36)
Recognized net actuarial loss 56 82
Net periodic benefit cost 123 149
Foreign Pension Plans    
Net periodic benefit cost:    
Service cost 113 110
Interest cost 76 84
Expected return on plan assets (125) (131)
Recognized net actuarial loss 49 46
Net periodic benefit cost $ 113 $ 109