Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.20%		4.20%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets			6.80%
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	$ 200
Net periodic benefit cost [Abstract]
Total amount amortized out of accumulated other comprehensive income	2,948	$ 3,021	$ 6,358	$ 6,022
Defined contribution plan expense	8,563	8,794	18,852	18,110
U.S. Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	2,303	3,021	5,287	6,042
Interest cost	5,153	5,430	10,255	10,859
Expected return on plan assets	(9,745)	(9,953)	(19,956)	(19,906)
Prior service cost (credit)	339	106	426	213
Recognized actuarial loss	870	1,395	2,801	2,791
Transition obligation	0	0	0	0
Net periodic (income)/expense	(1,080)	(1)	(1,187)	(1)
Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	1,534	1,343	3,111	2,660
Interest cost	1,343	1,285	2,721	2,549
Expected return on plan assets	(2,037)	(1,833)	(4,128)	(3,637)
Prior service cost (credit)	(111)	(112)	(226)	(222)
Recognized actuarial loss	782	864	1,585	1,705
Transition obligation	1	1	2	2
Net periodic (income)/expense	1,512	1,548	3,065	3,057
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	660	618	1,355	1,236
Interest cost	808	1,019	1,701	2,038
Prior service cost (credit)	1,351	1,103	2,314	2,205
Recognized actuarial loss	(281)	(298)	(536)	(596)
Net periodic (income)/expense	2,538	2,442	4,834	4,883
Post-Retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	7	8	15	17
Interest cost	72	73	145	146
Prior service cost (credit)	4	2	7	4
Recognized actuarial loss	(7)	(40)	(15)	(80)
Net periodic (income)/expense	76	43	152	87
Net periodic (income) expense [Member] | U.S. Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	273	846	950	1,692
Net periodic (income) expense [Member] | Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	73	203	247	405
Net periodic (income) expense [Member] | Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	97	306	351	613
Net periodic (income) expense [Member] | U.S. Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	(1,353)	(847)	(2,137)	(1,693)
Net periodic (income) expense [Member] | Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	1,439	1,345	2,818	2,652
Net periodic (income) expense [Member] | Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Net periodic (income)/expense	$ 2,441	$ 2,136	$ 4,483	$ 4,270