Divestitures and assets held for sale (Details) (USD $)	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash proceed from divestiture	$ 7,525,000	$ 1,041,000	$ 55,427,000
Net sales	0	0	203,202,000
Loss before income taxes	(345,000)	(28,000)	(8,845,000)
Divestitures [Line Items]
Loss before income taxes	345,000	28,000	8,845,000
Manufacturing plants in China [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss before income taxes	(700,000)
Divestitures [Line Items]
Number of manufacturing plants and related equipment sold	3
Loss before income taxes	700,000
Cash deposits received from divestiture	6,100,000
Carrying value of remaining assets recorded in assets-held for sale related to sale of manufacturing plants	5,700,000
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		1,800,000
Electrical [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other income recorded for updated estimates of the net proceeds upon disposition		600,000
Costs incurred in connection with the sale of business		600,000
Net cash proceed from divestiture			53,300,000
Medtech [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash proceed from divestiture	$ 300,000