Segment and Geographic Data, Revenue and assets by geographic area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 674,489	$ 677,883	$ 644,892	$ 606,258	$ 570,819	$ 591,955	$ 590,051	$ 570,606	$ 2,603,522	$ 2,323,431	$ 2,300,488
Property and equipment, net	905,758				848,871				905,758	848,871
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									590,638	542,506	560,973
Property and equipment, net	99,993				94,589				99,993	94,589
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									839,984	746,657	719,246
Property and equipment, net	154,874				120,223				154,874	120,223
Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									99,327	83,744	88,553
Property and equipment, net	130,523				112,953				130,523	112,953
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									11,292	10,007	12,597
Property and equipment, net	102,890				104,824				102,890	104,824
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									1,062,281	940,517	$ 919,119
People's Republic of China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	192,521				183,158				192,521	183,158
Republic of China (Taiwan) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	122,080				124,724				122,080	124,724
Other Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	99,493				105,400				99,493	105,400
Other Geographic Area [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 3,384				$ 3,000				$ 3,384	$ 3,000