Income taxes (Details) (USD $)	6 Months Ended
	Jun. 29, 2013	Dec. 31, 2012	Jun. 30, 2012
Income Tax Disclosure [Text Block]
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 2,500,000
Deferred Tax Assets, Valuation Allowance	6,000,000
Deferred Tax Assets, Net of Valuation Allowance, Current	724,000	962,000
Operating Loss Carryforwards			$ 39,400,000