Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net periodic benefit cost [Abstract]
Total amount amortized out of accumulated other comprehensive income	$ 3,049	$ 3,698	$ 9,071	$ 11,087
Defined contribution plan expense	9,569	8,153	31,766	26,310
U.S. Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	3,021	3,478	9,063	10,435
Interest cost	5,429	5,762	16,288	17,285
Expected return on plan assets	(9,953)	(9,698)	(29,859)	(29,095)
Prior service cost (credit)	107	184	320	550
Recognized actuarial gain	1,396	1,610	4,187	4,828
Transition obligation	0	0	0	0
Net periodic expense	0	1,336	(1)	4,003
Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	1,399	1,389	4,059	4,167
Interest cost	1,332	1,334	3,881	4,103
Expected return on plan assets	(1,885)	(1,899)	(5,522)	(5,821)
Prior service cost (credit)	(115)	(100)	(337)	(299)
Recognized actuarial gain	894	670	2,599	2,010
Transition obligation	1	1	3	3
Net periodic expense	1,626	1,395	4,683	4,163
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Net periodic benefit cost [Abstract]
Service cost	619	740	1,855	2,219
Interest cost	1,019	1,317	3,057	3,951
Prior service cost (credit)	1,103	1,567	3,308	4,700
Recognized actuarial gain	(298)	(141)	(894)	(421)
Net periodic expense	2,443	3,483	7,326	10,449
Post-Retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	8	13	25	39
Interest cost	74	105	220	314
Prior service cost (credit)	2	(35)	6	(107)
Recognized actuarial gain	(41)	(58)	(121)	(177)
Net periodic expense	$ 43	$ 25	$ 130	$ 69