Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Components of Net periodic pension cost for the Company's defined benefit pension plans and U.S. post-retirement medical plan
Service cost, net	$ 4,129	$ 4,262
Interest cost on projected benefit obligations	3,164	3,958
Expected return on plan assets	(9,006)	(10,346)
Net amortization and deferral	(2,074)	(1,730)
Recognition of actuarial losses/(gains)	7,113	5,690
Net periodic pension cost/(credit)	3,326	1,834
United States Pension Plans of US Entity, Defined Benefit [Member]
Components of Net periodic pension cost for the Company's defined benefit pension plans and U.S. post-retirement medical plan
Service cost, net	141	117
Interest cost on projected benefit obligations	1,094	1,292
Expected return on plan assets	(1,684)	(2,099)
Net amortization and deferral	0	0
Recognition of actuarial losses/(gains)	1,639	1,890
Net periodic pension cost/(credit)	1,190	1,200
Foreign Pension Plans, Defined Benefit [Member]
Components of Net periodic pension cost for the Company's defined benefit pension plans and U.S. post-retirement medical plan
Service cost, net	3,988	4,145
Interest cost on projected benefit obligations	2,052	2,647
Expected return on plan assets	(7,322)	(8,247)
Net amortization and deferral	(1,879)	(1,261)
Recognition of actuarial losses/(gains)	5,947	4,473
Net periodic pension cost/(credit)	2,786	1,757
Net Periodic Benefit Cost (Textuals) [Abstract]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	18,900
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Components of Net periodic pension cost for the Company's defined benefit pension plans and U.S. post-retirement medical plan
Service cost, net	0	0
Interest cost on projected benefit obligations	18	19
Expected return on plan assets	0	0
Net amortization and deferral	(195)	(469)
Recognition of actuarial losses/(gains)	(473)	(673)
Net periodic pension cost/(credit)	(650)	$ (1,123)
Net Periodic Benefit Cost (Textuals) [Abstract]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	$ 500