Divestitures and assets held for sale (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 29, 2013	Dec. 28, 2012 Plant
Manufacturing plants in China [Member]
Divestitures [Line Items]
Number of manufacturing plants and related equipment sold		3
Gain from sale of assets held for sale	$ 0.2	$ 0.7
Cash deposits received from divestiture		6.1
Carrying value of remaining assets recorded in assets-held for sale related to sale of manufacturing plants		5.7
Land and building in Tunisia [Member]
Divestitures [Line Items]
Carrying value of remaining assets recorded in assets-held for sale related to sale of manufacturing plants	$ 1.7