Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net periodic benefit cost [Abstract]
Total amount amortized out of accumulated other comprehensive income	$ 3,410	$ 3,001
Defined contribution plan expense	12,710	11,358
U.S. Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	2,984	3,021
Interest cost	5,102	5,429
Expected return on plan assets	(10,211)	(9,953)
Prior service cost (credit)	87	107
Recognized actuarial loss	1,931	1,396
Transition obligation	0	0
Net periodic (income)/expense	(107)	0
Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	1,577	1,317
Interest cost	1,378	1,264
Expected return on plan assets	(2,091)	(1,804)
Prior service cost (credit)	(115)	(110)
Recognized actuarial loss	803	841
Transition obligation	1	1
Net periodic (income)/expense	1,553	1,509
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	695	618
Interest cost	893	1,019
Prior service cost (credit)	963	1,102
Recognized actuarial loss	(255)	(298)
Net periodic (income)/expense	2,296	2,441
Post-Retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	8	8
Interest cost	73	73
Prior service cost (credit)	3	2
Recognized actuarial loss	(8)	(40)
Net periodic (income)/expense	$ 76	$ 43