Intangible assets, net (Details) (USD $)	3 Months Ended
	Mar. 29, 2013	Mar. 30, 2012	Dec. 28, 2012
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	$ 5,300,000		$ 5,300,000
Accumulated amortization	(4,950,000)		(4,833,000)
Net intangible assets subject to amortization	350,000		467,000
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, net	2,950,000		3,067,000
Weighted average life of finite intangible assets	1 year
Amortization expense for period	100,000	100,000
Tradename [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization (indefinite lives)	2,600,000		2,600,000
Customer relationships [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	3,300,000		3,300,000
Accumulated amortization	(2,950,000)		(2,833,000)
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	2,000,000		2,000,000
Accumulated amortization	$ (2,000,000)		$ (2,000,000)