Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	$ 4,193	$ 4,129
Defined Benefit Plan, Interest Cost	3,300	3,164
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	9,719	9,006
Defined Benefits Plan Net amortization and deferral	1,887	2,074
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(6,698)	(7,113)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	2,585	3,326
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	25,900
Pension Plan [Member] | Domestic Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	272	141
Defined Benefit Plan, Interest Cost	1,061	1,094
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	1,732	1,684
Defined Benefits Plan Net amortization and deferral	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(1,451)	(1,639)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1,052	1,190
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	3,921	3,988
Defined Benefit Plan, Interest Cost	2,223	2,052
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	7,987	7,322
Defined Benefits Plan Net amortization and deferral	1,794	1,879
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(5,560)	(5,947)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1,923	2,786
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	0	0
Defined Benefit Plan, Interest Cost	16	18
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	0	0
Defined Benefits Plan Net amortization and deferral	93	195
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	313	473
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(390)	$ (650)
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 400