Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Sep. 30, 2018
Operations of the Company's operating segments
Net Sales to External Customers	$ 690,673	$ 731,366	$ 1,339,835	$ 1,410,818
Revenue Transactions With Other Operating Segments	0	0	0	0
Net Sales	690,673	731,366	1,339,835	1,410,818
Segment Profit	176,643	177,741	317,921	325,582
Goodwill	537,624		537,624		$ 535,979	$ 534,557
US Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	249,340	267,889	490,750	502,540
Revenue Transactions With Other Operating Segments	27,515	26,571	53,904	52,716
Net Sales	276,855	294,460	544,654	555,256
Segment profit	52,581	53,986	97,519	91,971
Goodwill	414,370		414,370			410,021
Swiss Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	28,948	31,358	60,844	64,935
Revenue Transactions With Other Operating Segments	142,487	151,931	295,336	305,662
Net Sales	171,435	183,289	356,180	370,597
Segment profit	48,248	48,613	102,158	102,135
Goodwill	22,830		22,830			22,157
Western European Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	149,051	163,681	302,376	329,587
Revenue Transactions With Other Operating Segments	39,699	39,212	81,413	83,257
Net Sales	188,750	202,893	383,789	412,844
Segment profit	30,345	22,229	54,452	47,954
Goodwill	84,975		84,975			86,749
Chinese Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	140,907	136,459	241,506	258,181
Revenue Transactions With Other Operating Segments	45,731	52,568	94,480	109,425
Net Sales	186,638	189,027	335,986	367,606
Segment profit	63,955	65,489	109,505	124,973
Goodwill	621		621			643
Other Operations [Member]
Operations of the Company's operating segments
Net Sales to External Customers	122,427	131,979	244,359	255,575
Revenue Transactions With Other Operating Segments	875	1,334	1,771	2,595
Net Sales	123,302	133,313	246,130	258,170
Segment profit	13,122	14,300	24,148	27,487
Goodwill	14,828		14,828			14,987
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	(256,307)	(271,616)	(526,904)	(553,655)
Net Sales	(256,307)	(271,616)	(526,904)	(553,655)
Segment profit	(31,608)	$ (26,876)	(69,861)	$ (68,938)
Goodwill	$ 0		$ 0			$ 0