Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operations of the Company's operating segments
Net Sales to External Customers	$ 721,996	$ 653,656	$ 1,382,817	$ 1,248,223
Revenue Transactions With Other Operating Segments	0	0	0	0
Net Sales	721,996	653,656	1,382,817	1,248,223
Segment Profit	169,286	147,406	308,832	273,939
Goodwill	536,407	483,757	536,407	483,757	$ 539,838
US Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	251,474	238,831	481,219	454,184
Revenue Transactions With Other Operating Segments	23,487	23,092	47,153	45,505
Net Sales	274,961	261,923	528,372	499,689
Segment profit	42,006	45,147	76,251	83,969
Goodwill	409,470	357,782	409,470	357,782
Swiss Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	32,154	32,287	64,619	62,034
Revenue Transactions With Other Operating Segments	148,959	131,347	292,541	258,899
Net Sales	181,113	163,634	357,160	320,933
Segment profit	47,737	37,950	93,712	73,968
Goodwill	21,787	22,544	21,787	22,544
Western European Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	173,772	151,161	339,144	298,484
Revenue Transactions With Other Operating Segments	45,141	43,883	86,153	86,825
Net Sales	218,913	195,044	425,297	385,309
Segment profit	27,333	24,709	45,615	49,427
Goodwill	89,412	87,388	89,412	87,388
Chinese Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	133,272	108,092	247,202	198,873
Revenue Transactions With Other Operating Segments	58,588	57,036	118,995	109,969
Net Sales	191,860	165,128	366,197	308,842
Segment profit	65,884	54,127	125,437	98,787
Goodwill	678	653	678	653
Other Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	131,324	123,285	250,633	234,648
Revenue Transactions With Other Operating Segments	1,463	2,129	3,103	3,726
Net Sales	132,787	125,414	253,736	238,374
Segment profit	17,642	15,181	31,523	28,289
Goodwill	15,060	15,390	15,060	15,390
Intersegment Elimination [Member]
Operations of the Company's operating segments
Net Sales to External Customers	0	0	0	0
Revenue Transactions With Other Operating Segments	(277,638)	(257,487)	(547,945)	(504,924)
Net Sales	(277,638)	(257,487)	(547,945)	(504,924)
Segment profit	(31,316)	(29,708)	(63,706)	(60,501)
Goodwill	$ 0	$ 0	$ 0	$ 0