Goodwill and intangible assets (Schedule of intangible assets subject to amortization) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 29, 2012	Oct. 01, 2011	Sep. 29, 2012	Oct. 01, 2011
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, beginning balance			$ 154,668
Amortization during the period	(15,683)	(17,746)	(47,942)	(53,120)
Currency translation during the period			(894)
Intangible assets subject to amortization, ending balance	105,832		105,832
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, beginning balance			64,958
Amortization during the period			(33,908)
Currency translation during the period			(171)
Intangible assets subject to amortization, ending balance	30,879		30,879
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, beginning balance			88,544
Amortization during the period			(13,943)
Currency translation during the period			(733)
Intangible assets subject to amortization, ending balance	73,868		73,868
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, beginning balance			1,166
Amortization during the period			(91)
Currency translation during the period			10
Intangible assets subject to amortization, ending balance	$ 1,085		$ 1,085