Pension and Non-pension Postretirement Benefits (Net Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,326	$ 1,313
Interest cost	4,087	4,449
Expected return on plan assets	(5,617)	(5,755)
Amortization of unrecognized:
Prior service cost (credit)	12	12
Actuarial loss / (gain)	1,490	1,322
Pension expense or non-pension postretirement benefit expense	1,298	1,341
Defined Benefit Plan, Contributions [Abstract]
Employer contributions made to defined benefit plans	1,300
Estimated employer contributions to defined benefit plans in remainder of 2017	1,300
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,075	996
Interest cost	3,450	3,777
Expected return on plan assets	(5,617)	(5,755)
Amortization of unrecognized:
Prior service cost (credit)	59	66
Actuarial loss / (gain)	1,352	1,120
Pension expense or non-pension postretirement benefit expense	319	204
Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	251	317
Interest cost	637	672
Expected return on plan assets	0	0
Amortization of unrecognized:
Prior service cost (credit)	(47)	(54)
Actuarial loss / (gain)	138	202
Pension expense or non-pension postretirement benefit expense	979	1,137
Non-Pension Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	220	199
Interest cost	592	664
Amortization of unrecognized:
Prior service cost (credit)	(50)	35
Actuarial loss / (gain)	12	9
Pension expense or non-pension postretirement benefit expense	774	907
Defined Benefit Plan, Contributions [Abstract]
Employer contributions made to defined benefit plans	600
Estimated employer contributions to defined benefit plans in year 2017	5,000
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	220	199
Interest cost	581	652
Amortization of unrecognized:
Prior service cost (credit)	(50)	35
Actuarial loss / (gain)	25	20
Pension expense or non-pension postretirement benefit expense	776	906
Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	11	12
Amortization of unrecognized:
Prior service cost (credit)	0	0
Actuarial loss / (gain)	(13)	(11)
Pension expense or non-pension postretirement benefit expense	$ (2)	$ 1