Annual report pursuant to Section 13 and 15(d)

Benefit Plans - Recognized on the Balance Sheet (Details)

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Benefit Plans - Recognized on the Balance Sheet (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Pension Plans | U.S.    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position    
Noncurrent asset $ 0 $ 0
Current liability 0 0
Noncurrent liability (42,728) (48,503)
Accumulated other comprehensive income (loss) 10,499 8,190
Net amount recognized (32,229) (40,313)
Defined Benefit Pension Plans | Foreign    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position    
Noncurrent asset 3,503 3,391
Current liability (673) (331)
Noncurrent liability (26,022) (22,940)
Accumulated other comprehensive income (loss) (2,871) (2,085)
Net amount recognized (26,063) (21,965)
Supplemental Retirement Plans    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position    
Current liability (1,115) (1,170)
Noncurrent liability (11,667) (12,055)
Accumulated other comprehensive income (loss) 573 623
Net amount recognized (12,209) (12,602)
Other Postretirement Benefits Plans    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position    
Current liability (561) (629)
Noncurrent liability (4,051) (3,991)
Accumulated other comprehensive income (loss) 885 877
Net amount recognized $ (3,727) $ (3,743)