Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Operations of the Company's operating segments
Net Sales to External Customers	$ 734,846	$ 698,799	$ 2,117,663	$ 1,947,022
Revenue Transactions With Other Operating Segments	0	0	0	0
Net Sales	734,846	698,799	2,117,663	1,947,022
Segment Profit	181,965	161,739	490,797	435,678
Goodwill	537,862	538,418	537,862	538,418	$ 539,838
US Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	255,379	239,221	736,598	693,405
Revenue Transactions With Other Operating Segments	25,050	24,187	72,203	69,692
Net Sales	280,429	263,408	808,801	763,097
Segment profit	41,890	43,004	118,141	126,973
Goodwill	410,022	409,172	410,022	409,172
Swiss Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	31,463	33,923	96,082	95,957
Revenue Transactions With Other Operating Segments	148,418	136,960	440,959	395,859
Net Sales	179,881	170,883	537,041	491,816
Segment profit	44,542	39,212	138,254	113,181
Goodwill	22,404	22,252	22,404	22,252
Western European Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	173,170	171,722	512,314	470,206
Revenue Transactions With Other Operating Segments	41,923	40,287	128,076	127,112
Net Sales	215,093	212,009	640,390	597,318
Segment profit	30,046	32,519	75,661	81,946
Goodwill	89,915	90,832	89,915	90,832
Chinese Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	140,098	125,067	387,301	323,940
Revenue Transactions With Other Operating Segments	64,079	68,625	183,074	178,593
Net Sales	204,177	193,692	570,375	502,533
Segment profit	75,762	69,086	201,199	167,873
Goodwill	644	673	644	673
Other Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	134,736	128,866	385,368	363,514
Revenue Transactions With Other Operating Segments	1,334	1,754	4,436	5,481
Net Sales	136,070	130,620	389,804	368,995
Segment profit	19,179	16,754	50,702	45,043
Goodwill	14,877	15,489	14,877	15,489
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	(280,804)	(271,813)	(828,748)	(776,737)
Net Sales	(280,804)	(271,813)	(828,748)	(776,737)
Segment profit	(29,454)	(38,836)	(93,160)	(99,338)
Goodwill	$ 0	$ 0	$ 0	$ 0

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