Quarterly report pursuant to Section 13 or 15(d)

Benefit Plans - Net Periodic Pension Expense Benefit (Details)

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Benefit Plans - Net Periodic Pension Expense Benefit (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Defined Benefit Pension Plans | U.S.        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost $ 305 $ 547 $ 914 $ 1,640
Interest cost 2,536 2,522 7,608 5,236
Expected return on plan assets (3,061) (3,104) (9,183) (6,176)
Net periodic expense (benefit) (220) (35) (661) 700
Defined Benefit Pension Plans | Foreign        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost 859 792 2,642 1,320
Interest cost 1,339 837 4,024 1,396
Expected return on plan assets (1,111) (769) (3,329) (1,283)
Net periodic expense (benefit) 1,087 860 3,337 1,433
Supplemental Retirement Plans        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Interest cost 123 121 370 202
Net periodic expense (benefit) 123 121 370 202
Other Postretirement Benefits Plans        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost 5 9 15 28
Interest cost 40 53 122 110
Amortization of prior service credit (19) 0 (58) 0
Amortization of net gain (19) 0 (58) 0
Net periodic expense (benefit) $ 7 $ 62 $ 21 $ 138