Net Periodic Benefit Cost (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Components of Net periodic pension cost for the Company's defined benefit pension plans and U.S. post-retirement medical plan
Service cost, net	$ 4,262	$ 4,954
Interest cost on projected benefit obligations	3,958	5,197
Expected return on plan assets	(10,346)	(11,693)
Net amortization and deferral	(1,730)	(1,442)
Recognition of actuarial losses/(gains)	5,690	4,883
Net periodic pension cost/(credit)	$ 1,834	1,899
Net Periodic Benefit Cost (Textuals) [Abstract]
Number of Employees offered Lump Sum Settlement of US Pension Plan	700
Defined Benefit Plan, Settlements, Benefit Obligation	$ 14,600
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	8,300
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	117	209
Interest cost on projected benefit obligations	1,292	1,608
Expected return on plan assets	(2,099)	(2,394)
Net amortization and deferral	0	0
Recognition of actuarial losses/(gains)	1,890	1,907
Net periodic pension cost/(credit)	1,200	1,330
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	4,145	4,745
Interest cost on projected benefit obligations	2,647	3,554
Expected return on plan assets	(8,247)	(9,299)
Net amortization and deferral	(1,261)	(973)
Recognition of actuarial losses/(gains)	4,473	3,819
Net periodic pension cost/(credit)	1,757	1,846
Net Periodic Benefit Cost (Textuals) [Abstract]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	19,400
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	19	35
Expected return on plan assets	0	0
Net amortization and deferral	(469)	(469)
Recognition of actuarial losses/(gains)	(673)	(843)
Net periodic pension cost/(credit)	(1,123)	$ (1,277)
Net Periodic Benefit Cost (Textuals) [Abstract]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	$ 500