Goodwill and intangible assets (Schedule of intangible assets subject to amortization) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2015	Sep. 27, 2014	Oct. 03, 2015	Sep. 27, 2014	Dec. 31, 2014
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance			$ 626,713
Intangible assets acquired during the period			224,326
Currency translation during the period			(37,711)
Intangible assets subject to amortization, ending balance	$ 813,328		813,328
Accumulated amortization, beginning balance			547,395
Amortization during the period	9,378	$ 6,140	20,748	$ 18,687
Currency translation during the period			(33,639)
Accumulated amortization, ending balance	534,504		534,504
Intangible assets subject to amortization, net	278,824		278,824		$ 79,318
Customer Relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance			354,768
Intangible assets acquired during the period			223,825
Currency translation during the period			(16,727)
Intangible assets subject to amortization, ending balance	561,866		561,866
Accumulated amortization, beginning balance			320,851
Amortization during the period			10,573
Currency translation during the period			(16,178)
Accumulated amortization, ending balance	315,246		315,246
Intangible assets subject to amortization, net	246,620		246,620
Patents [Member]
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance			270,466
Intangible assets acquired during the period			0
Currency translation during the period			(20,984)
Intangible assets subject to amortization, ending balance	249,482		249,482
Accumulated amortization, beginning balance			225,875
Amortization during the period			10,170
Currency translation during the period			(17,468)
Accumulated amortization, ending balance	218,577		218,577
Intangible assets subject to amortization, net	30,905		30,905
Other [Member]
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance			1,479
Intangible assets acquired during the period			501
Currency translation during the period			0
Intangible assets subject to amortization, ending balance	1,980		1,980
Accumulated amortization, beginning balance			669
Amortization during the period			5
Currency translation during the period			7
Accumulated amortization, ending balance	681		681
Intangible assets subject to amortization, net	$ 1,299		$ 1,299