Goodwill and Other Intangible Assets (Net intangible assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets, Net:
Cost	$ 810,332	$ 838,764
Acquisitions	3,175	0
Currency translation	85,550	(28,432)
Accumulated amortization	651,498	555,873
Net Value	247,559	254,459	$ 304,192
Customer relationships
Intangible Assets, Net:
Cost	569,980	588,716
Acquisitions	3,175	0
Currency translation	52,108	(18,736)
Accumulated amortization	390,428	334,276
Net Value	234,835	235,704	271,123
Patents
Intangible Assets, Net:
Cost	234,022	243,258
Acquisitions	0	0
Currency translation	32,947	(9,236)
Accumulated amortization	259,908	220,598
Net Value	7,061	13,424	$ 26,985
Other
Intangible Assets, Net:
Cost	6,330	6,790
Acquisitions	0	0
Currency translation	495	(460)
Accumulated amortization	1,162	999
Net Value	$ 5,663	$ 5,331